Career Highlights: Merritt has dominated the 400 meter and 4x400 relay events since winning three gold medals (also taking the 4x100 relay) at the 2004 world junior championships. He accumulated six more golds before the 2008 Olympics, when he again finished first in his top two events, setting a personal best with a time of 43.75 seconds in the 400 and winning by a record margin. He followed that a year later by again winning gold in both events in the world championships, but Merritt’s continued dominance took an unplanned break when he was banned for two years in April 2010 after it was revealed he’d failed three drug tests. Merritt claimed those resulted from his use of the over-the-counter penis enlargement product ExtenZe, which contains a banned steroid. That penalty was eventually reduced to 21 months and Merritt came back strong in 2011, winning silver in the 400m and gold in the 4x400 relay. There’s little doubt the gold is Merritt’s to lose in London after he blitzed the competition at the U.S. Olympic trials in June, finishing in 44.12 seconds. Americans have swept the medals in the 400 in the last two Olympics, but Merritt won’t have to worry about his longtime rival in this installment. Jeremy Wariner, who won gold in Athens in 2004 before being edged out by Merritt four years ago in Beijing, failed to qualify in the 400.