No official announcement was made and interim coach Tom Cable did not mention it during his daily meeting with the media, but Walker told reporters Thursday that his season is over after injuring his left ankle during Oakland's 17-6 loss to Carolina last Sunday.
Walker was not at practice but walked into the Raiders' locker room using a pair of crutches and wearing a high protective boot on his left foot.
"I'm done for the season," Walker said. "They've got to put some screws in."
The Raiders were able to walk away from DeAngelo Hall's $72 million contract after paying Hall $8 million because his contract was guaranteed only for injury, not skill, but it won't be that easy for Oakland with Walker.
According to Walker's agent, Kennard McGuire, the wideout has an injury guarantee in his contract for guaranteed money in the second year of the deal. Walker received an $11 million signing bonus and a $1 million base salary at the outset of his $55 million deal. But the season-ending ankle injury that was revealed Thursday could put Oakland on the hook for most, if not all, of a $5 million roster bonus that he's scheduled to make next March.
Walker injured himself while making a 14-yard reception in the second quarter against the Panthers. He limped off the field but later returned to make another catch in the second half.
Although Walker finished the game, he was unable to practice Wednesday and was taken for tests Thursday. Cable, who is trying to find a way to end Oakland's three-game losing streak, had not spoken with Walker and was unaware of the receiver's status, a team spokesman said.
The three catches against Carolina raised Walker's season total to 15 in nine games, disappointing numbers for a player the Raiders hoped would anchor their passing game when they signed him to a $55 million, six-year deal in the offseason.
Walker had been criticized by then-coach Lane Kiffin for being out of shape during offseason workouts, was seriously injured in June during a robbery in Las Vegas, contemplated retirement early in training camp and then sat out Oakland's season-opening loss to Denver due to a hamstring injury.
The news wasn't all bad for Oakland, though.
Quarterback JaMarcus Russell took most of the snaps with the starting offense in practice Thursday and will likely be back in the lineup after sitting out the loss to Carolina with a bruised knee. The timing is fortunate because backup Andrew Walter, who started against the Panthers, was unable to practice due to a high ankle sprain.
"[Russell] was good today," Cable said. "He was much better and took the majority of reps in practice."
Rookie running back Darren McFadden, who has been sidelined with turf toe injuries, was also cleared to play for the first time since Oct. 19.
"I'm ready to go," McFadden said. "I've been feeling real nice the last two days of practice, just being able to go out there and run and not have pain. At first just walking on it was hard on me, but then as that went away it was trying to cut the burst and the cuts."
Two-time Pro Bowl defensive end Derrick Burgess was given the day off and is likely to miss his sixth straight game while recovering from a triceps strain. Burgess had practiced Wednesday for the first time since getting hurt in practice Oct. 6.
"Because he's been out awhile, obviously there's some fatigue," Cable said.
Strong safety Gibril Wilson (lower back) was limited in practice. ... Cable said the team is undecided whether to use Johnnie Lee Higgins or recently signed Justin Miller to return kickoffs against Miami this week.
John Clayton is a senior writer for ESPN.com. Information from the Associated Press was used in this report