He stopped around the time of the Twins second home run, certainly by the third.
Here's the thing: Ground balls aren't that good for hitters.
According to Fangraphs's data (numbers from 2014):
(ISO is "isolated power" -- the difference between batting average and slugging percentage, or how many extra bases the hits are gaining. wOBA is "weighted onbase average," which I won't attempt to explain because linear weights make my head hurt, but is said by sabermetricans to be an effective measurement of offensive production. My understanding is that the new Twins front office uses wOBA rather than OPS.)
The point is pretty obvious: You want to hit line drives. There is a slightly higher batting average on ground balls than flyballs, but flyballs are a lot more productive because darn few grounders turn into home runs.
The Twins had one groundout against Zimmermann on Tuesday (4.2 innings). They scored five runs. They had four groundouts gainst Shane Greene (two innings). They scored zero.
I am reminded of a line in "Pennant Race," Jim Brosnan's journal of the 1961 Cincinnati Reds unlikely pennant winning season. The Reds are in a slump, the team is having a players only meeting, and somebody says: If you gotta hit a ground ball, knock the second baseman over with it.
Hit the ball hard, good things will happen