LaShawn Merritt (C) of the U.S. takes the baton from teammate Jeremy Wariner for the final leg of the men's 4x400 relay race at the IAAF World Relays Championships in Nassau Bahamas, May 3, 2015.The U.S. won the gold medal in the event. REUTERS/Mike Segar 

The U.S. men's 4x400 relay team celebrate with their gold medals after winning the race at the IAAF World Relays Championships in Nassau Bahamas, May 3, 2015. From left are David Verburg, Tony McQuay, Jeremy Wariner and LaShawn Merritt. REUTERS/Mike Segar 

Jeremy Wariner takes the lead before winning the finals of the men's 400 meter dash at the USA Indoor Track and Field Championships in Albuquerque, New Mexico March 3, 2013. REUTERS/Eric Draper (UNITED STATES - Tags: SPORT ATHLETICS) 

Jeremy Wariner studies the track before running in the finals of the men's 400 meter dash at the USA Indoor Track and Field Championships in Albuquerque, New Mexico March 3, 2013. Wariner placed first in the event. REUTERS/Eric Draper (UNITED STATES - Tags: SPORT ATHLETICS TPX IMAGES OF THE DAY) 

Jeremy Wariner and Marcus Boyd (back) compete in the qualifying round of the men's 400 meter dash at the USA Indoor Track and Field Championships in Albuquerque, New Mexico March 2, 2013. REUTERS/Eric Draper (UNITED STATES - Tags: SPORT ATHLETICS) 

U.S. athlete Jeremy Wariner stretches before training at the U.S. Olympic athletics trials in Eugene, Oregon June 21, 2012. REUTERS/Mike Blake (UNITED STATES - Tags: SPORT ATHLETICS OLYMPICS) 

Jeremy Wariner reacts after placing sixth in the men's 400 meter final at the U.S. Olympic athletics trials in Eugene, Oregon, June 24, 2012. REUTERS/Lucy Nicholson (UNITED STATES - Tags: SPORT OLYMPICS ATHLETICS) 

Jeremy Wariner reacts after placing sixth in the men's 400 meter final at the U.S. Olympic athletics trials in Eugene, Oregon, June 24, 2012. REUTERS/Lucy Nicholson (UNITED STATES - Tags: SPORT OLYMPICS ATHLETICS) 

Runner Jeremy Wariner competes in the first round of qualifying for the men's 400 meters during the U.S. Olympic athletics trials in Eugene, Oregon June 22, 2012. REUTERS/Robert Galbraith (UNITED STATES - Tags: SPORT ATHLETICS OLYMPICS) 

Runner Jeremy Wariner runs during first round of qualifying for the men's 400 meters at the U.S. Olympic athletics trials in Eugene, Oregon, June 22, 2012. Former Games gold medallist Wariner was 13th fastest of 16 qualifiers. He ran 45.84. REUTERS/Lucy Nicholson (UNITED STATES - Tags: SPORT OLYMPICS ATHLETICS) 

Runner Jeremy Wariner runs during qualifying for the men's 400 meters at the U.S. Olympic athletics trials in Eugene, Oregon June 22, 2012. REUTERS/Steve Dipaola (UNITED STATES - Tags: SPORT ATHLETICS OLYMPICS) 

Runner Jeremy Wariner (L) runs during qualifying for the men's 400 meters at the U.S. Olympic athletics trials in Eugene, Oregon June 22, 2012. REUTERS/Steve Dipaola (UNITED STATES - Tags: SPORT ATHLETICS OLYMPICS) 

Runners Manteo Mitchell (L-R), Torrin Lawrence, and Jeremy Wariner finish first, second and third respectively during qualifying for the men's 400 meters at the U.S. Olympic athletics trials in Eugene, Oregon, June 22, 2012. REUTERS/Lucy Nicholson (UNITED STATES - Tags: SPORT OLYMPICS ATHLETICS) 

Sprinters Jeremy Wariner and Oscar Pistorius (R) speak during a press conference in New York, June 8, 2012. REUTERS/Keith Bedford (UNITED STATES - Tags: SPORT ATHLETICS) 

Sprinters Jeremy Wariner and Oscar Pistorius (R) speak during a press conference in New York, June 8, 2012. REUTERS/Keith Bedford (UNITED STATES - Tags: SPORT ATHLETICS) 

Sprinters Jeremy Wariner and Oscar Pistorius (R) speak during a press conference in New York, June 8, 2012. REUTERS/Keith Bedford (UNITED STATES - Tags: SPORT ATHLETICS) 

Jeremy Wariner starts the men's 400 meters heat at the U.S. Outdoor Track and Field Championships in Eugene, Oregon June 23, 2011. REUTERS/Steve Dipaola(UNITED STATES - Tags: SPORT ATHLETICS) 

Jeremy Wariner (L) of the U.S. crosses the finish line ahead of Rondell Bartholomew of Grenada during the men's 400 metres event at the New York Diamond League Grand Prix athletics meet June 11, 2011. REUTERS/Brendan McDermid (UNITED STATES - Tags: SPORT ATHLETICS) 

Jeremy Wariner of the U.S. celebrates after winning the men's 400 metres event at the IAAF Diamond League athletics meeting at the Letzigrund stadium in Zurich August 19, 2010. REUTERS/Arnd Wiegmann (SWITZERLAND - Tags: SPORT SPORT ATHLETICS)

Jeremy Wariner of the U.S. celebrates after winning the men's 400 metres event at the IAAF Diamond League athletics meeting at the Letzigrund stadium in Zurich August 19, 2010. REUTERS/Ruben Sprich (SWITZERLAND - Tags: SPORT SPORT ATHLETICS)

Jeremy Wariner of the U.S. celebrates after winning the men's 400 metres event at the IAAF Diamond League athletics meeting at the Letzigrund stadium in Zurich August 19, 2010. REUTERS/Arnd Wiegmann (SWITZERLAND - Tags: SPORT SPORT ATHLETICS)

Jeremy Wariner of the U.S. celebrates after winning the men's 400 metres event at the IAAF Diamond League athletics meeting at the Letzigrund stadium in Zurich August 19, 2010. REUTERS/Ruben Sprich (SWITZERLAND - Tags: SPORT SPORT ATHLETICS)

Jeremy Wariner (R) of the U.S. competes ahead of Jermane Gonzales of Jamaica to win the men's 400 metres event at the IAAF Diamond League athletics meeting at the Letzigrund stadium in Zurich August 19, 2010. REUTERS/Ruben Sprich (SWITZERLAND - Tags: SPORT SPORT ATHLETICS)

Jeremy Wariner (R) of the U.S. wins the men's 400m race during the London Grand Prix Diamond League athletics tournament at Crystal Palace in London August 14, 2010. REUTERS/Paul Hackett (BRITAIN - Tags: SPORT ATHLETICS IMAGES OF THE DAY) 

Jeremy Wariner (2nd R) of the U.S. wins the men's 400m race during the London Grand Prix Diamond League athletics tournament at Crystal Palace in London August 14, 2010. REUTERS/Paul Hackett (BRITAIN - Tags: SPORT ATHLETICS) 

Jeremy Wariner of the U.S. wins the men's 400m race during the London Grand Prix Diamond League athletics tournament at Crystal Palace in London August 14, 2010. REUTERS/Paul Hackett (BRITAIN - Tags: SPORT ATHLETICS) 

Jeremy Wariner (L-R) of the U.S. runs to win ahead of second placed compatriot Lajerald Betters and Jermaine Gonzales of Jamaica in the men's 400m competition at the IAAF Diamond League athletics meeting at the Stade de la Pontaise in Lausanne July 8, 2010. REUTERS/Valentin Flauraud (SWITZERLAND - Tags: SPORT ATHLETICS)

Jeremy Wariner (L) of the U.S. runs to win ahead of second placed compatriot Lajerald Betters in the men's 400m competition at the IAAF Diamond League athletics meeting at the Stade de la Pontaise in Lausanne July 8, 2010. REUTERS/Michael Buholzer (SWITZERLAND - Tags: SPORT ATHLETICS)

Jeremy Wariner of the U.S. celebrates his victory in the men's 400m competition at the IAAF Diamond League athletics meeting at the Stade de la Pontaise in Lausanne July 8, 2010. REUTERS/Michael Buholzer (SWITZERLAND - Tags: SPORT ATHLETICS)

Jeremy Wariner of the U.S. celebrates his victory in the men's 400m competition at the IAAF Diamond League athletics meeting at the Stade de la Pontaise in Lausanne July 8, 2010. REUTERS/Denis Balibouse (SWITZERLAND - Tags: SPORT ATHLETICS)

Jeremy Wariner of the U.S. celebrates his victory in the men's 400m competition at the IAAF Diamond League athletics meeting at the Stade de la Pontaise in Lausanne July 8, 2010. REUTERS/Denis Balibouse (SWITZERLAND - Tags: SPORT ATHLETICS)

Jeremy Wariner of the U.S. reacts after winning the 400m Men event at the IAAF Diamond League athletics meeting in Rome June 10, 2010. REUTERS/Giampiero Sposito (ITALY - Tags: SPORT ATHLETICS) 

Jeremy Wariner of the U.S. (R) crosses the finish line to win the 400m Men event ahead of fellow countryman Angelo Taylor at the IAAF Diamond League athletics meeting in Rome June 10, 2010. REUTERS/Giampiero Sposito (ITALY - Tags: SPORT ATHLETICS) 

Jeremy Wariner of the U.S. (C) crosses the finish line to win the 400m men's race at the IAAF Diamond League athletics meeting in Rome June 10, 2010. REUTERS/Ciro De Luca (ITALY - Tags: SPORT ATHLETICS) 

Jeremy Wariner of the U.S. (R) crosses the finish line to win the 400m men's race at the IAAF Diamond League athletics meeting in Rome June 10, 2010. REUTERS/Ciro De Luca(ITALY - Tags: SPORT ATHLETICS) 

Jeremy Wariner of the U.S. wins the men's 400 metres race at the IAAF Golden League Memorial Van Damme athletics meeting in Brussels September 4, 2009. REUTERS/Sebastien Pirlet (BELGIUM SPORT ATHLETICS) 

Jeremy Wariner of the U.S. adjusts his glasses at the start of the men's 400 metres race at the IAAF Golden League Memorial Van Damme athletics meeting in Brussels September 4, 2009. REUTERS/Sebastien Pirlet (BELGIUM SPORT ATHLETICS) 

LaShawn Merritt (L) runs past Jeremy Wariner, both from the U.S., to win the men's 400 meters race during the IAAF Golden League athletics meeting at the Letzigrund stadium in Zurich, August 28, 2009. REUTERS/Michael Buholzer (SWITZERLAND SPORT ATHLETICS IMAGES OF THE DAY) 

(From L to R) LaShawn Merritt, Angelo Taylor, Jeremy Wariner and Kerron Clement of the U.S. celebrate their gold medal during the medal ceremony for the men's 4x400 metres relay at the world athletics championships in Berlin August 23, 2009. REUTERS/Martin Rose/Pool (GERMANY SPORT ATHLETICS) 

Jeremy Wariner of the U.S. (R) passes the baton to team mate Kerron Clement the 4x400 meters relay final during the world athletics championships at the Olympic stadium in Berlin, August 23, 2009. REUTERS/Dominic Ebenbichler (GERMANY SPORT ATHLETICS) 

Jeremy Wariner of the U.S. (R) passes the baton to team mate Kerron Clement the 4x400 meters relay final during the world athletics championships at the Olympic stadium in Berlin, August 23, 2009. REUTERS/Dominic Ebenbichler (GERMANY SPORT ATHLETICS) 

Angelo Taylor of the U.S. passes the baton to team mate Jeremy Wariner (R) in the 4x400 meters relay final during the world athletics championships at the Olympic stadium in Berlin, August 23, 2009. REUTERS/Max Rossi (GERMANY SPORT ATHLETICS) 

Renny Quow of Trinidad and Tobago displays his medal during the awards ceremony for the men's 400 metres at the world athletics championships at the Olympic stadium in Berlin August 22, 2009. LaShawn Merritt of the U.S. won the gold, ahead of compatriot Jeremy Wariner who won silver and Quow who won bronze. REUTERS/Wolfgang Rattay (GERMANY SPORT ATHLETICS) 

Jeremy Wariner of the U.S.displays his medal during the awards ceremony for the men's 400 metres at the world athletics championships at the Olympic stadium in Berlin August 22, 2009. LaShawn Merritt of the U.S. won the gold, ahead of compatriot Wariner who won silver and Renny Quow of Trinidad and Tobago who won bronze. REUTERS/Wolfgang Rattay (GERMANY SPORT ATHLETICS) 

LaShawn Merritt of the U.S. displays his medal during the awards ceremony for the men's 400 metres at the world athletics championships at the Olympic stadium in Berlin August 22, 2009. Merritt won the gold, ahead of Jeremy Wariner of the U.S.who won silver and Renny Quow of Trinidad and Tobago who won bronze. REUTERS/Wolfgang Rattay (GERMANY SPORT ATHLETICS) 

Jeremy Wariner of the U.S., campatriot LaShawn Merritt , Renny Quow of Trinidad and Tobago (L-R) display their medals during the awards ceremony for the men's 400 metres at the world athletics championships at the Olympic stadium in Berlin August 22, 2009. Merritt won the gold, ahead of Wariner who won silver and Quow who won bronze. REUTERS/Wolfgang Rattay (GERMANY SPORT ATHLETICS) 

LaShawn Merritt of the U.S. (lane 4) crosses the finish line ahead of (L to R) Michael Bingham of Britain, second placed compatriot Jeremy Wariner, Tabarie Henry of the Virgin Islands, Chris Brown of Bahamas, third placed Renny Quow of Trinidad and Tobago, David Gillick of Ireland and Leslie Djhone of France in the men's 400 meters final during the world athletics championships at the Olympic stadium in Berlin, August 21, 2009. REUTERS/Tobias Schwarz (GERMANY SPORT ATHLETICS) 

LaShawn Merritt of the U.S. (R) crosses the finish line ahead of compatriot Jeremy Wariner (L) in the men's 400 meters final during the world athletics championships at the Olympic stadium in Berlin, August 21, 2009. REUTERS/Fabrizio Bensch (GERMANY SPORT ATHLETICS) 

Jeremy Wariner of the U.S. walks on the track after taking second place in the men's 400 meters final during the world athletics championships at the Olympic stadium in Berlin, August 21, 2009. REUTERS/Max Rossi (GERMANY SPORT ATHLETICS) 

Jeremy Wariner of the U.S. celebrates after winning the second place in the men's 400 metres final during the world athletics championships at the Olympic stadium in Berlin August 21, 2009. REUTERS/Phil Noble (GERMANY SPORT ATHLETICS) 

Jeremy Wariner of the U.S. walks on the track after taking second place in the men's 400 meters final during the world athletics championships at the Olympic stadium in Berlin, August 21, 2009. REUTERS/Tobias Schwarz (GERMANY SPORT ATHLETICS) 

Jeremy Wariner of the U.S. hold up his national flag as he celebrates after the men's 400 metres final during the world athletics championships at the Olympic stadium in Berlin August 21, 2009. REUTERS/Kai Pfaffenbach (GERMANY) 

Jeremy Wariner of the U.S. celebrates after winning the second place in the men's 400 metres final during the world athletics championships at the Olympic stadium in Berlin August 21, 2009. REUTERS/Tobias Schwarz (GERMANY SPORT ATHLETICS) 

Jeremy Wariner of U.S. talks to Renny Quow of Trinidad and Tobago (R) as they cover themselves with their national flags after the men's 400 metres final during the world athletics championships at the Olympic stadium in Berlin August 21, 2009. REUTERS/Kai Pfaffenbach (GERMANY) 

Jeremy Wariner of the U.S. (L) and Renny Quow of Trinidad and Tobago celebrate after the men's 400 metres final during the world athletics championships at the Olympic stadium in Berlin August 21, 2009. REUTERS/Kai Pfaffenbach (GERMANY SPORT ATHLETICS) 

LaShawn Merritt (2nd R) of the U.S. leads Jeremy Wariner (L) of the U.S., Chris Brown (2nd L) of the Bahamas and Renny Quow (R) of Trinidad and Tobago to the finish line winnnig the men's 400 meters final during the world athletics championships at the Olympic stadium in Berlin, August 21, 2009. REUTERS/Michael Dalder (GERMANY SPORT ATHLETICS) 

LaShawn Merritt (L) of the U.S. celebrates after winning ahead of compatriot Jeremy Wariner in the men's 400 metres final during the world athletics championships at the Olympic stadium in Berlin, August 21, 2009. REUTERS/Kai Pfaffenbach (GERMANY) 

LaShawn Merritt (R) of the U.S. finishes to win ahead of compatriot Jeremy Wariner in the men's 400 metres final during the world athletics championships at the Olympic stadium in Berlin, August 21, 2009. REUTERS/Kai Pfaffenbach (GERMANY) 

LaShawn Merritt (2R) of the U.S. finishes to win ahead of compatriot Jeremy Wariner, Britain's Michael Bingham and Tabarie Henry of Virgin Islands (L-R) in the men's 400 metres final during the world athletics championships at the Olympic stadium in Berlin, August 21, 2009. REUTERS/Phil Noble (GERMANY) 

Jeremy Wariner of the U.S. competes with Ramon Miller (L) of Bahamas in the men's 400 metres semi-final heats during the world athletics championships at the Olympic stadium in Berlin, August 19, 2009. REUTERS/Dominic Ebenbichler (GERMANY)