LONDON — For American Meb Keflezighi, prerace introductions in the men’s marathon on Sunday morning provided motivation. Race organizers separated 10 marathoners, including American Ryan Hall, from the rest of the field and gave them individual introductions.

The group consisted of runners believed to be the top medal contenders, as well as the best British entrant. Despite a silver medal at the 2004 Athens Olympics and a first-place finish in the 2009 New York City Marathon, Keflezighi was not included. And that perceived snub pushed him to fourth place in 2 hours, 11 minutes and 6 seconds, a very satisfying finish considering injuries derailed his training this spring.