He worked well with Santana in 2006. He's only had one remotely decent season since.
At this point in his career it's time to stop remembering his 12-3 season where he was lights out. Instead, he's a pitcher who has posted a 5+ ERA in 3 of his past 4 seasons, has a WHIP sitting around 1.5, gets murdered by right handers, gets his 9 SO/9 but he counters that with 5 BB/9, and averages just over 5 IP per start which will KILL our bullpen.
I would argue this is more than "struggling a bit lately". Maybe as a reliever, but the walks are so high I don't see a fit there either.