The Miami Dolphins' running back, ninth on the NFL's career rushing list, was hurt while making a cut on a reception in the Dolphins' 17-7 victory at San Diego on Sunday.
The 34-year-old Thomas will do some rehabilitation work over the next month before deciding whether to have surgery, Miami coach Dave Wannstedt said Monday.
Thomas, who missed 11 games last year with a bruised liver, was unavailable for comment because Wannstedt gave the players the day off. But after the game Sunday, the 13-year veteran said he might think about ending his career if the injury was serious.
"It's a concern for me if I'm looking at 10 months of rehab," he said. "I might have to consider retirement."
He said he was emotional as the pain got worse on the sideline.
"It flashed through my mind for the first time in 13 years," he said. "I started to cry a little bit."
Thomas starred with the Buffalo Bills for his first 12 seasons and was voted the NFL's Most Valuable Player after the 1991 season. He was the Dolphins' third-down back.
In his first year with Miami (8-2), Thomas had 28 rushes for 136 yards and 16 receptions for 117 yards. He has 12,074 career yards, 46 short of Franco Harris, who is eighth.
"It's very disappointing for Thurman," Wannstedt said. "I think he really was enjoying himself and was having fun being part of something that's off to a pretty decent start."
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