“I want to have the energy and the will to keep passing people during the race,” he said.

Dean, 32, of Alexandria, Va., has run 12 marathons in his career. His best time came in Chicago in 2003 when he posted a time of 2:33:32.

Dean, however, was not the first choice at Ferris Baker Watts. That distinction went to Mike Fox-Boyd, 27, a teacher and track coach at The Queen Anne School.

“I was approached in the spring by Robin [Oegerle] from FBW,” Fox-Boyd said.

Three weeks ago, Fox-Boyd suffered a severe stress fracture in his left tibia. Looking for a replacement, Fox-Boyd contacted Dean, a friend from the D.C. Roadrunners club, and offered him the opportunity.

“He?s run like a billion marathons, and he?s faster than me,” Fox-Boyd said. “We run together and trained together a lot.”

Already training for another marathon, Dean was not concerned about his fitness entering today?s race. Rather, his concern was how to approach passing so many people in a grueling endurance event like a marathon.

Weaving through a crowd can drain a lot of energy needed to complete a 26.2-mile run. Aware of this, Fox-Boyd shared tips with Dean from one of his test runs during an Annapolis race earlier this year.

“First couple miles, getting past the large crowd will be tough,” said Dean, who will be wearing a distinctive green shirt during the race. “Their pace will be different than what I want to run.”

Finishing in the top quarter of several thousand racers might sound daunting, but Dean sees it as a very simple goal.

“Pass as many people as possible,” he said.