Harvin sprained his ankle in the second half of Sunday's loss to the Seattle Seahawks and was on crutches Monday when he declared himself a "long shot" to play but was still holding out hope.
Despite the doubtful designation, Vikings coach Leslie Frazier wasn't ready to completely rule Harvin out.
"Still has a little less than 48 hours to continue to improve. He'll continue to get treatment. If it comes to it, we would definitely work him out before the game to get him out there, if that's possible," Frazier said.
"He'd have to make quite a bit of recovery (Saturday) for us to say, ‘OK, we'll wait until Sunday to see what you can do.' But it's possible. We've seen it happen before. We're going to continue to treat him and see how he does tomorrow."
On Thursday, Harvin walked through the locker room slowly with a pronounced limp, but he no longer had the crutches that accompanied him Monday.
Harvin leads the NFL with 62 catches. He also leads the league with a 35.9-yard kickoff return average.
Rookie receiver Jarius Wright, a fourth-round pick, will be active for the first time in his career whether or not Harvin can play, according to Frazier.
Marcus Sherels would take Harvin's turns in the kickoff return game if Harvin is unable.
The Vikings did get running back Adrian Peterson back on the practice field Friday after he left Winter Park Thursday morning with a stomach virus. He is expected to play Sunday and said Friday he was feeling much better.
"Yesterday morning as soon as I woke up, my stomach felt like it was cramping, like it was balled up," Peterson said. "I threw up before I even got here. Once I got here, I was just kind of hunched over, not really feeling good, feeling weak."
Peterson, who was listed as probable, leads the league with 957 rushing yards and is second among running backs with a 5.7-yard average per carry. He is also coming off his third straight game with at least 100 yards rushing.
He had 182 yards on 17 carries in a loss to the Seattle Seahawks on Sunday. He also had 123 yards (on 15 carries) and 153 yards (on 23 carries) over a five-day span in the previous two games against the Tampa Bay Buccaneers and Arizona Cardinals.
The Vikings have the 30th-ranked passing offense and fifth-ranked rushing offense in the league.
Defensive tackle Letroy Guion (turf toe) also returned to practice on a limited basis, but, like Harvin, he is doubtful.
"He moved around a little bit in some of the drills we had, just to be able to get a feel for where he was so we kind of gauge the probability of his maybe playing," Frazier said. "We got an idea of where he is; now it's just a matter of how much he improves tomorrow and before Sunday."
Fred Evans will start if Guion doesn't play, Frazier said. NOTES
Tim Yotter is the publisher of Viking Update. Follow Viking Update on Twitter and discuss this topic on our message boards. To become a subscriber to the Viking Update web site or magazine, click here.