Can't think of a pitcher who is mentally weaker than Niese. . . .
I disagree. I think it's physical weakness. Ever since he started complaining of shoulder problems last year, his velocity has dropped and his vaunted curveball has completely disappeared. He's relegated to trying to hit corners, change speeds and stay out of the strike zone. In other words, he needs to be a different pitcher than what he was, and the chances of that working out are never good.
So he nibbles. Guys walk. Hitters get into 3-1, 2-0 and 3-2 counts with men on base. And he still tries to nibble because he really doesn't want to give hitters something to hit with men on base. So it worsens. And then eventually he comes in and gets hit. And, even sometimes, he doesn't need to come into the strike zone to get his because his stuff can be so soft.
When pitchers lose velocity, even if they weren't flamethrowers to start with, their effectiveness almost always goes down with it. That's what's happened to Neise. He wasn't a nibbler when he came up. He was a guy who regularly threw 92-93, had a hard cutter, and had possibly the best curve ball in the game. He's nothing like that anymore. It's physical.