Harvin, who last year led the team in every receiving category, was reportedly becoming one of the team leaders and seemed to be one of the more content players even through the disappointing 2011 season.
The first thought that comes to mind is his contract situation. Harvin, going into his fourth season in the NFL, is still playing under his five-year rookie contract. Harvin is set to make only $915,000 this upcoming season and $1.55m in 2013. Harvin has established himself as one of the elite playmakers in the league, even if he's not a prototypical No.1 wide receiver. He has certainly earned himself a new contract, increasing his stat totals in each of his three seasons even though the quarterback play has gotten steadily worse.
But, the Vikings also realize this, and I find it hard to believe that they wouldn't renegotiate with Harvin. He's one of the few elite players on the team, and they certainly would realize that Harvin has earned a better contract. So it must be something else in addition to the contract.
Harvin has stated recently that he is unhappy with multiple issues, and that they "definitely" need to be taken care of prior to training camp later this summer or he may not attend.
During this offseason, the team has added a lot of players for the passing game, signing free agents WR Jerome Simpson and TE John Carlson and adding WRs Greg Childs and Jarius Wright in the draft. With WR Micheal Jenkins and TE Kyle Rudolph also on the team currently, there appears to be a lot of players fighting for receptions in an offense that doesn't pass very much.
Additionally, it must be noted that this all came about during and right after OTAs. Harvin doesn't seem to fit into offensive coordinator Bill Musgrave's offensive style. Musgrave is hoping to create a two-TE base offense for the Vikings, and a slot type receiver like Harvin is not typically featured much in that style of play. It could be possible that Harvin saw what the offense will look like in OTAs and realized that he won't be getting a lot of snaps this fall.
Harvin is a fan favorite with the Vikings and an emerging star in the league. After last year's 3-13 season, the Vikings cannot afford to have more bad press and fans certainly would not want to see Harvin leave. It would be unlikely that the Vikings will grant the trade request, but whatever the problems are with Harvin, they better hope it gets taken care of before training camp becomes yet another of the seemingly annual soap operas that the Vikings have.