Every time Heyward has one or two games where he looks like he might be headed in the right direction, he follows that up with five or six games that look worse than ever.
I'm not saying Chapman shouldn't have stayed in, but this game is much more important to the Cardinals than it is to the Cubs. The Cubs had the luxury of choosing not to do what the Cardinals had to do.
I could be completely wrong, but my non-expert opinion is that Chapman's body language in the dugout indicated he told them he didn't want to pitch a 2nd inning.