Simpson will miss 3 games with suspension for getting arrested for marijuana, but he was a solid #2 receiver in Cincinnati last year with 50 catches for 725 yards and 4 touchdowns. I mentioned this when I mocked Matt Kalil to the Vikings over Morris Claiborne. The Vikings priority of this year (since they aren’t going to win a lot of games no matter what) should be to figure out if they have a keeper or not in Christian Ponder at quarterback.
You simply can’t fairly evaluate Ponder with the lack of offensive supporting cast he had last year. Simpson gives him another weapon and more importantly a veteran weapon because young receivers tend to struggle out of the gate (AJ Green and Julio Jones aside). They’ll only have him for 13 games, but they aren’t paying him much at all (2 million over a year) so this was a worthwhile investment.