What's the rest of your team look like? I would say NO on the surface, as Upton is likely to be a top 5 player within 4 years. Kershaw could be a top 5 SP then though. But where Kershaw would help you in Ks, ERA and WHIP (his WHIP was a solid 1.23 despite the walks), he will hurt you in BB. At this point, Upton definitely has Runs, Net SB, OBP and SLG over Carlos Lee (who I assume would be replacing him in your lineup), and it's at best a tossup between Upton and Lee in HR and RBI, and that's if Lee is healthy and remembers how to hit.