Clinton Portis said Tuesday that he hoped to play this weekend against the Minnesota Vikings. One day later, his season came to an early end for the second year in a row.
"He was just a big part of this football team," Shanahan said. "You hate to see a person work that hard and not get an opportunity to finish the season. And he was ready to play, and he did play. He played exceptionally well."
The new injury is just above the area of the torn left groin that caused Portis to miss five games earlier this season. Portis returned from the groin injury for Sunday's game against the Tennessee Titans, but he lasted just five carries before being hurt again.
While an MRI exam didn't reveal any further damage to Portis's torn groin, The Washington Post reported it did show "something new above the area that he [initially] tore," Shanahan said.
Shanahan told reporters he informed Portis of the decision Tuesday night, after Dr. James Andrews, the Redskins' senior orthopedic consultant, told the coach that surgery would be needed, according to The Post.
Portis will require at least two months of rehabilitation, ending his season with a career-low 227 yards on 54 carries with two touchdowns.
"It's a huge blow," Redskins rookie left tackle Trent Williams said, via The Post. "He's one of the leaders on this offense and somebody who everybody looked up to because he's been getting it done for a (lot) of years. It's tough for the game, but we got to keep ticking."
The move also could end Portis' career with the Redskins after seven seasons. The 29-year-old running back is 77 yards short of 10,000 for his career and 648 yards shy of John Riggins' franchise record.
Portis missed the last eight games of the 2009 season with a severe concussion, and the Redskins brought in veterans Willie Parker and Larry Johnson to challenge him for playing time this season. Parker and Johnson eventually were cut, then youngsters Ryan Torain and Keiland Williams took over the bulk of the running back duties after Portis first hurt his groin during an Oct. 3 game against the Philadelphia Eagles.
Torain isn't expected to play Sunday against the Vikings because of a hamstring injury, leaving Williams as the starter and James Davis and Andre Brown as the likely backups. Davis was promoted from the practice squad Monday, and Brown will be signed if he passes a physical.
Portis has three years left on his contract, but his salary would increase to $8.25 million in 2011. Shanahan said he has no doubts that Portis can still play in the NFL.
"He's got such a strong will. It all depends on 'Does he come back 100 percent?' 'Does he want to come back and play?"' Shanahan said. "Because he's got that inner drive that most people don't have. But obviously he's got to get well."
Shanahan said he isn't second-guessing whether or not Portis returned from the groin injury too soon. The coach said Portis was ready to play the week before, but he was held back as a precaution.
"How do you know for sure?" Shanahan said. "You've just got to go with your gut and see how a guy practices, and he practiced really well, so who knows for sure?"
In another roster move, the Redskins signed offensive lineman Jacob Bender to the practice squad.
The Associated Press contributed to this report.