The St. Louis Cardinals currently have six starters and only four spots in the playoff rotation, so there's a good chance that Jake Westbrook and Lance Lynn will be demoted to the bullpen. Chris Carpenter, Adam Wainwright, Kyle Lohse and Jaime Garcia would then comprise the rotation.
Harper and Carpenter have never faced off, as Carpenter was on the shelf for most of this season with an injury.
When they do finally go against each other, expect Carpenter to have the advantage. His veteran know-how will trump Harper's free-swinging tendencies and lead to a couple of strikeouts for the rookie.
3-5, 1 2B, 1 BB
Harper has owned Wainwright in six plate appearances against him. Some of those hits came at a time when Wainwright was not really himself, however. Earlier this season, he was struggling to get back to his pre-Tommy John surgery form.
Now that he's nearly back to his normal self, look for the tides to turn a bit.
3-6, 1 2B, 1 K
Lohse has been great for the Cardinals this season, so it's probably safe to discount the few times he has surrendered base hits to Harper.
A veteran pitcher like himself should know how to handle Harper in the playoffs. If he makes a mistake, though, look out.
1-3, 1 HR, 2 RBI
In terms of run production, Harper has fared the best against Garcia out of all the other pitchers listed in this slideshow.
That's only after one game, though. Being a lefty, Garcia could feasibly give Harper some trouble in the playoffs. This will be an interesting matchup to watch.