Harvin was hit with his latest string of migraine headaches on Dec. 1, when he was limited in practice. Since then, he hasn't practiced and missed the Vikings' 38-14 win over the Buffalo Bills on Sunday.
"One of the things that they're taking a look at is trying to find out, is there something that might be triggering the migraines?" interim head coach Leslie Frazier said. "And they're doing a lot of things to try to get to the bottom of it and lessen the number of times it happens or the frequency of it. So, that's kind of where it is."
Sunday was the second game Harvin missed in his career. He also missed a game last December against the Cincinnati Bengals because of migraines. Harvin also had a serious bout with them in August, when he collapsed on the Vikings' practice field after a reaction to migraine-related medication he was taking and was taken to the hospital in an ambulance.
"When he has those episodes, you don't always know how long they're going to last or the severity of those migraines, and every one is somewhat different but still somewhat the same," Frazier said. "But nobody can deal with it other than the person who's having those migraines. In my case, I end up going by what the doctors tell me and also when I communicate with Percy, what he tells me. Right now, no football for right now."
Frazier said he talked to Harvin on Thursday and planned on speaking again on Friday, but just before officially listing Harvin as doubtful, Frazier didn't sound optimistic.
"It's going to be touch-and-go. We're going to talk again (Friday). But it's going to be very, very difficult to get him up to speed," Frazier said.
It would be the first time in his two-year career that Harvin has missed back-to-back games, and the first time he's missed two games in a season.
Harvin remains the Vikings' leading receiver, catching 51 passes for 627 yards and four touchdowns in his 11 games played.
While Harvin is doubtful, there is no debating the availability of cornerback Chris Cook (knee) or safety Tyrell Johnson (knee), who were both declared out for Sunday's game. Frazier said there has been some internal discussion about shutting down Cook for the season, but Cook said no one has approached him with that possibility yet.
Cooks has been dealing with inflammation and "dull pain" in his left knee, the most of recent of two to be operated on for meniscus tears.
In addition to Harvin, Cook and Johnson, QB Brett Favre (shoulder), guard Steve Hutchinson (thumb), defensive end Ray Edwards (ankle) and QB Joe Webb (hamstring) are questionable.
After playing 123 consecutive games, Hutchinson's fractured thumb could shut him down for the second straight game.
"He has a very tough injury because of the position that he plays," Frazier said of Hutchinson's thumb. "It's just a matter of can he mentally get past some things that he's have to get past. Based on what we've seen, it's going to be difficult because the position he plays requires using your hands every single snap. So it's going to be tough, but if anybody can do it, Steve Hutchinson can do it."
Wide receivers Bernard Berrian (groin), Sidney Rice (hip) and Greg Lewis (concussion), running backs Toby Gerhart (hamstring) and Adrian Peterson (ankle), and safety Jamarca Sanford (hamstring) are all probable, meaning they are a virtual certainty to play.
TOO FAR REMOVED
Vikings cornerback Frank Walker spent his first four seasons in the NFL playing for the New York Giants, but he said those days are so far removed that he can't offer the Vikings much of a scouting report on their opponent Sunday.
"I'm five years removed. A lot of things change in four or five years," Walker said, but he added, "For the most part, I see a lot of the same stuff on film. Coach (Kevin) Gilbride has been the offensive coordinator the whole time and the quarterbacks coach."
When Walker was with the Giants, the receivers were Ike Hilliard, Amani Toomer, David Tyree and Willie Ponder, so while he might recognize the formations, that doesn't offer him any insight into the players' strengths and weaknesses.
Despite not being with the Giants since 2006, Walker still says the organization holds a place in his heart.
"Absolutely. That's the team that drafted me," he said.
"That was probably as good a Friday practice as we've had in a while. The guys were really into it," Frazier said. "Great energy, great focus, it was good work. Really gets you excited about the direction that we're going as a group. We've got to go out and play a very good football team on Sunday, but you can't fault the effort of our group."
Asked what it would be like if Rice reached his stride just as the Vikings' season ended, Rice said, "That would suck. I would hate that. Like I said, everything's been feeling like it's getting better every week."
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.