I already looked at the good side of the Matt Kemp acquisition. Unfortunately, there is a bad side too. The bad side can mostly be summed up in one word: defense. Matt Kemp came up as a CF and has thought of himself as a CF. Unfortunately he cannot play CF adequately enough to not be hindrance to his club. I don't want to reinvent the wheel here trying to analyze his defense because others have done it enough already. The easiest stat to look at with horror is the negative value he tallied in defensive WAR last season. If you pull up his baseball-reference page you can see that value was -3.1. His offensive value was 3.8. His defense was so bad that it almost negated all of his offensive value.
That's not to say he'll be that bad in 2014. Taking him out of CF (and hopefully the Padres will keep him away from CF) and moving him to a corner OF spot (I assume RF, but it could be LF) will help. However, even will the move you can't remove all the negative value out there. It will still transform him from being a solidly above average baseball player to a close to average one. The offense will still be helped, but some runs will be given back in the field.
This may be hard for some after already day dreaming about his offensive value. And I really don't want to discourage you from getting excited about the added offense to a team that had next to none. But when it comes to wins and losses, everything matters. And the value of a solo home run can be taken away by bad reads on balls like this when there's a runner in scoring position:
And Kemp isn't getting any younger. There are already signs that he's lost a significant amount of speed and athleticism and he's only going to be 30 years old this season. That has happened to other young stars (see: Wells, Vernon) with ugly results. And we've seen first hand with Carlos Quentin how injuries can take a toll on a player as he enters his 30s. Here's hoping Kemp can stave off father time during the length of this contract.