While Favre watched from the sideline because of post-concussion symptoms, Webb helped the Vikings upset the playoff-bound Philadelphia Eagles on Tuesday. The sixth-round draft pick from Alabama-Birmingham completed 17 of 26 passes for 195 yards and also ran for 31 yards and a touchdown, without any turnovers.
Still, Vikings interim coach Leslie Frazier said Favre will start Sunday against the Detroit Lions if he can participate.
"We'd love to see him play," Frazier said Wednesday. "It's really not a hard decision for me. Brett is a terrific player. We feel very comfortable when he's on the field that we have a great chance to win, so you always want to put the guy out there who is going to give you the best chance to win. If Brett is healthy, I think our entire team feels very confident that we have a great chance to win when he's the starting quarterback."
Frazier praised Webb for his poise down the stretch against the Eagles, including a critical third-and-11 completion to Percy Harvin with less than 8½ minutes left, putting the Vikings in position for a touchdown that stretched their lead to 10 points.
"Everyone kept telling me they've got my back," Webb said after the game, adding: "I just wanted to make sure, first, I took care of the ball and put my team in place to win."
Webb said he won't worry about whether or not he will receive another start.
"I'm just playing my game and just having fun with it," he said. "Whatever coach wants to do with me, that's his decision. All I can do is play and perform to the best of my ability."
Webb credited Favre for giving him valuable advice on the sideline and seemed to have a grasp of the situation this week -- that one of the sport's all-time greats is on the verge of playing his last game.
"If he wants to play, he can play," Webb said. "He's Brett Favre."
The Vikings didn't practice Wednesday, but they issued an injury report that said Favre wouldn't have participated. The Star Tribunelater cited league sources in reporting that Favre took a concussion test Wednesday afternoon but didn't pass.
Before the Star Tribune report came out, Frazier said the 41-year-old quarterback hadn't taken a concussion test in "three or four" days, but he might give them another go Thursday. Last year, the NFL issued stricter return-to-play standards regarding head injuries.
"You're trying to get a gauge of how close he is to what he was before," Frazier said. "And then after that, you've got to be able to find out if the guy can exercise without symptom. You've got to put him through a few different drills just to find out if he's headache-free, he's not experiencing dizziness or nausea or some of the things that you sometimes get when you have a guy that was concussed."
Frazier said the team's medical staff has told him there are no concerns about Favre's shoulder, neck or hand, the injuries that kept him out of the Dec. 13 game against the New York Giants and ended his NFL-record streak of 297 consecutive regular-season starts.
"He's a very competitive guy, as we all know," Frazier said. "I approached him last night in pregame. We were watching the offense warm up, and I said, 'Hey, I know those competitive juices are flowing, aren't they?' He started laughing and said, 'Yes they are.' And that's not going to change. It's just a matter of if he can physically do it or not. He'd like to finish on the football field as opposed to watching. That's just who he is."
As for Webb, the Vikings and their fans would enjoy another chance to watch him play before the season is over, too. He's the only quarterback currently on the roster under contract beyond this year, and his status -- he was originally slated to play wide receiver -- will be one of many intriguing offseason storylines for this unsettled franchise.
"He has a high ceiling," Frazier said. "He's a tremendous athlete, a guy who's very charismatic. Players really rally behind Joe. They have a lot of confidence in his abilities. Although he's a very young player, they really believe in him, and it's been that way all along."
The Vikings (6-9) put constant pressure on Michael Vick and touted Frazier, their aspiring permanent head coach, with perhaps their best performance of the season. Frazier said he expects to speak with team owner Zygi Wilf and president Mark Wilf soon about his status. Frazier received a congratulatory phone call from them after the game.
"They were really pleased with the way our players played and the effort that they gave, and they were very complimentary," Frazier said.
Notes: Frazier said RB Adrian Peterson will be closely watched this week after hurting his knee but finishing the game Tuesday. ... Favre won't be the only player subject to post-concussion testing this week. WR Sidney Rice and backup LB Erin Henderson also had concussions against the Eagles. FS Madieu Williams is still recovering from his from the previous week.
The Associated Press contributed to this report.