The concern now for Winborn, and obviously for 49ers officials as well, is whether his latest injury also might end the third-year veteran's career.
Knocked backward during a play in Wednesday's practice, Winborn felt a tingling in his arm as he went back to the huddle, and an MRI exam on Thursday revealed that he has a herniated disk between the C-5 and C-6 vertebrae. For now, surgery is not recommended, but doctors will continue to monitor Winborn's condition.
The team placed Winborn on injured reserve on Friday and signed free agent linebacker Cornelius Anthony, who had been with the 49ers in training camp. Winborn spent all but three games of the 2002 season on injured reserve because of a knee injury.
"This [injury] is probably more serious, from the long-term standpoint, but every time you get hurt it's frustrating," said Winborn, a second-round pick in the 2001 draft who has been limited to just 26 appearances because of his injuries. "You feel like you're just letting everybody down: the team, your family, yourself. But I'm determined [to come back]."
Although not officially listed as a starter, Winborn plays nearly as many snaps as the San Francisco first-unit linebackers, and his loss will force the 49ers to scramble. Second-year veteran Saleem Rasheed will replace Winborn but the former Alabama standout, who has played primarily on special teams this season, has big shoes to fill.
Winborn, 24, typically plays in some "base" situations at the "plugger" position, but he is more involved in "nickel" packages, where he is superb in coverage and a surprisingly effective blitzer as well. The presence of Winborn on the field on third down contributes to the excellence of strongside linebacker Julian Peterson, regarded as one of the league's premier defenders in 2003.
In nine games, Winborn has 37 tackles and three sacks.
"He's has the same value to us as a starter," coach Dennis Erickson said of Winborn. "He is a huge part of what we do."
An articulate player who is well-grounded, Winborn is aware of the seriousness nature of his back injury and will be "very involved," he said, in the evaluation process.
The former Vanderbilt star might be fortunate that 49ers trainers recommended the MRI exam after Winborn complained of soreness in his back. Winborn was prepared just to be treated by a chiropractor and planned to play in Monday's game against Pittsburgh. The training staff insisted a more thorough evaluation was necessary.
"I know the [implications] of what may have happened if I had played [with the injury]," Winborn said. "In that sense, even with all the frustrations, I'm grateful."