Zack Greinke is returning to the Royals, at age 39. He's pretty much a non-factor at this point, having gone 3-9 with a 3.68 ERA, striking out just 73 in 137 innings. He did manage to allow 0-2 runs in 17/26 starts last year, which is consistent with his career. He's been one of the better pitchers over time at avoiding getting bombed, presumably because he does not get emotionally rattled by runs scoring against him.

Greinke was one of the best pure athletes of MLB pitchers, consistently being one of the best hitting pitchers (back when that was allowed) and also winning Gold Glove awards.

He has social anxiety, which caused him to miss an entire season of MLB early in his career, and he considered quitting altogether. I also believe he has Aspergers, though this has never formally been stated. I actually think the Aspergers is what helps him distance himself emotionally from the frustration of allowing early runs in games.

His best years were with the Dodgers.