MIAMI -- Ricky Williams' latest comeback lasted one game.
The Miami Dolphins running back will miss the rest of the season with a torn chest muscle, according to his agent, Leigh Steinberg.
Williams was injured on Monday at Pittsburgh, when he played in his first game in nearly two years. He returned following a 1 1/2-year suspension for his latest violation of the NFL drug policy.
Steinberg said the arm will be in a sling from four to six weeks and the rehab will take five months.
But Steinberg said Williams expects to be ready for next season.
"It's sad given how hopeful Ricky had been about his return to football and given the amount of effort Ricky had put into his rehabilitation. But he's optimistic and hopeful for the future."
With a winless record, the Dolphins were desperate for help and eager to showcase Williams in hopes of increasing his trade value. Coach Cam Cameron decided to play Williams only a week after he joined practice.
"My No. 1 concern coming into the game, when you hurry a guy back, obviously he could get hurt," Cameron said after the game.
Williams was injured in the second quarter Monday on a play when he fumbled. After being tackled, he was accidentally stepped on while chest-down on the ground.
Williams left the game, returned briefly and departed for good after one more carry. He finished with 15 yards in six carries, and the Dolphins lost 3-0 on a last-minute field goal.
Williams, the 2002 NFL rushing champion, has played in only 13 games since retiring in the summer of 2004. He has tested positive for marijuana at least four times since the Dolphins acquired him in 2002, and their franchise-record playoff drought began that same year.
Williams hasn't missed an NFL game because of an injury since 2000 when he was with the New Orleans Saints.
Copyright 2007 by The Associated Press