D.C. United midfielder Josh Gros, 25, will not play this year after suffering three head injuries in 2007.
"He does not plan to play the 2008 season due to the effects of his many concussions," Dan Segal, Gros's agent, wrote in an e-mail to the Washington Post. "He has made no other decisions about the future."
Gros, who has been a starter for most of his four seasons in MLS, recently accepted a job at an engineering firm and is undecided about his long-term future. In 101 career regular season starts, Gros has nine goals and 14 assists for D.C.
Last spring, during a match in Mexico, Gros experienced headaches, dizziness and blurred vision after getting hit on the head with the ball. He only missed one game, but in August, a similar episode sidelined him for a further four games. Another spell in Mexico in October ended his season, and Gros has since visited specialists in Washington, Pittsburgh and Concord, Mass.