David DeJesus is an interesting player. Although he's never hit more than 13 home runs in a season, he's always been a pretty useful player. He is not a prototypical RF because he has little power, but he's not a prototypical leadoff guy because he has no speed. He's a true #2 hitter; David will put the ball in play, move a guy over, and get on base.
DeJesus signed a 2 year, 8.5 million contract with a 2014 team option at 6.5 (1.5 buyout). The reason DeJesus was to be had so cheaply was the appearance of a dwindling skillset: his OBP crashed from .384 to .323 in just one season. That doesn't tell the whole story, though; the primary driver of that descent was an abnormally high and then low BABIP (.355 in 2010, .274 in 2011). The Cubs were willing to take a gamble on the aberrant nature of DeJesus' BABIP, and it paid off...kinda.
DeJesus got on base 35% of the time last year, which is a pretty good number and in line with the rest of his career numbers. Unfortunately, the power from 2010 has more or less eroded. A .403 SLG from RF is untenable unless you are a defensive mastermind, which DeJesus is not. For David to have more than just average value, he'll have to recoup some power or get on base with a greater frequency; home runs might not happen but DeJesus has some gap power.
DeJesus' primary value comes from his ability to extend plate appearances and get on base. He sports a career .355 OBP and 8.6% walk rate. That means that while he walks the same as a normal player, he consistently has a BABIP in the .315 range, making his batting average 15 points higher than the league average. If his BABIP were to fall to .300, he'd be essentially league average in every way (save lower power), but after 3305 AB we can be confident that .315 hovers around his true value.
DeJesus doesn't strike out all that often; his career rate is 13.6%, 4% less than the league average. The fact that he maintains a low strikeout rate while going deep into at-bats is a huge, hidden bonus on offense and makes him the ideal #2 hitter in a line-up. He swings at less pitches than the average, and makes contact with pitches at a much, much higher rate than normal. That's the trademark of a hitter that is not only intelligent, but consistent as well. DeJesus will likely be good for longer than is normal.
DeJesus plays best, by far, in left field. He doesn't have a great arm in right, but for some reason he's always had a good noodle in left, and is range is much improved there is well. He plays a passable centerfield as well, and in another era that'd be where is most useful; right now, there is a glut of talent at CF in the big leagues, so his positional flexibility isn't as useful per se. He won't kill you at any spot in the outfield, but as you go from left to right, as a rule he's less and less useful to a club.
David DeJesus is a smart, consistent player. I'm a big fan of the guy, and could see him being a hitting coach in the future. His best days are probably behind him, though. His age-33 season is coming up, and he does have value to a team that needs a cheap outfielder with an extra year of team control. The contract is worth 10 million over 2 years, and he should give you 2 WAR each year for the next 2. That's a similar value to Alfonso Soriano; a back-end of a team's top 10 prospects or a few live arms. I'd probably hold off on trading DeJesus if you trade Soriano and slot him at left (someone has to play there, right?). He'd make a mighty fine, affordable, midseason trade chip, and I believe that's what the Cubs will do.