A day after he collapsed on the practice field, Percy Harvin remains hospitalized for precautionary reasons in Minnesota.
Harvin's continuous bouts with migraines have raised concerns regarding how much he will be able to contribute this season. Suddenly, one of the Super Bowl favorites might find itself without one of its biggest weapons.
Here's a look at 10 possible effects Harvin's absence could have on the Vikings.
Percy Harvin was second on the Vikings in receptions as a rookie, catching 60 passes for 790 yards and six touchdowns.
Although he was not officially a starter, Harvin proved to be a much more reliable option for Brett Favre than Bernard Berrian, who is an effective deep-route runner but has little impact in the short passing game.
If Harvin isn't cleared to play this season, the Vikings will find themselves looking for a player who brings both speed and the ability to work as an effective slot receiver in the offense.
Although not many people knew for certain how valuable Harvin would become to the Vikings as a receiver, everyone knew his impact on the return game would be huge.
As a rookie, Harvin recorded 1,156 return yards and returned two kicks for touchdowns. He routinely gave the offense good starting field position and represented another headache for opponents.
The Vikings will likely turn to rookie Ray Small to bolster the return game in the preseason in hopes of finding an insurance policy if Harvin isn't able to return.
Throughout his NFL career, Brett Favre has made a habit out of spreading the ball around to all his receivers, tight ends, and running backs.
If Harvin is unable to return, Favre would likely be forced to rely heavily on Sidney Rice, his favorite target last season. With Rice unlikely to play in the preseason and Harvin's status up in the air, Favre could be working with a patchwork group of players going into the season.
Harvin's big-play ability made it easier for the Vikings to protect Favre by throwing short passes or screens and relying on yards after the catch to move the ball. If Harvin isn't able to go, Favre will be forced to stay in the pocket longer to try to make things happen downfield.
The Vikings were already very thin at receiver heading into the season, and Harvin's migraine issues make a bad situation even worse.
Sidney Rice is recovering from hip surgery and might not be up to full speed early in the regular season. Bernard Berrian is a decent player who can take it the distance, but he isn't overly effective at going over the middle.
The rest of the receiving corps features a handful of young, unproven players including Taye Biddle and Marquis Hamilton.
Minnesota would be wise to look to make a move, perhaps for the Bengals Quan Cosby, who can play receiver and return kicks.
If Harvin is either unable to play or severely limited, the Vikings will need to account for over 2,000 yards of total offense.
It will have to be a complete team effort.
In an ideal scenario for embattled coach Brad Childress, the Vikings would hand the ball to Adrian Peterson 35 times and let him do his thing. That might give the team the best chance to win early in the season until the problems at receiver are sorted out.
In the return game, Ray Small showed an ability to thrive in that role during an inglorious career at Ohio State marred by suspensions. The undrafted rookie has the speed and natural talent to become a solid kick returner, but prior to Harvin's incident he wasn't even considered a lock to make the team.
Harvin's medical history has been well documented, and the Vikings have done everything to take his health into consideration.
The frightening incident Thursday will bring everything the Vikings have done under the microscope, especially if Harvin is unable to return to the field.
According to ESPN's Rachel Nichols, several of Harvin's teammates had questioned the repeated illnesses that kept Harvin out of the first two weeks of training camp.
After what happened Thursday, most people are expecting the worst. If Harvin manages to make it back to the field and contribute consistently, his teammates are certain to develop a great deal of respect for his toughness.
Until recently, the NFL had done everything in its power to dispute the findings of any and all studies suggesting head injuries create potentially devastating long-term effects.
The NFL has finally recognized the problem and is making strides to aggressively study the effects of concussions.
Harvin's constant problems with migraines can't be traced to a single concussion. The problem has plagued him throughout his life, including even before he began his college career at Florida.
It will be interesting to see if the Vikings or the NFL attempt to take a closer look at what is behind Harvin's headaches.
Oddly enough, Harvin's collapse at practice came on the same day that a Yahoo! report claimed that Favre was reluctant to return because he had no faith in Vikings coach Brad Childress. The report claimed that many of the Vikings players share these alleged sentiments.
Before Childress has to face the probing questions from the media, he had to address the Harvin situation. The feud will continue to be a story, but for the moment at least, it has taken a backseat to Harvin's cloudy future.
Percy Harvin produced one of the best all-around seasons of any rookie in NFL history and was destined to continue an ascension towards stardom.
Now, it appears his career could be in jeopardy.
There have been no indications as of yet regarding Harvin's prognosis. It seems unlikely that he will see any action in the preseason, and what happens beyond that is anybody's guess.