Rocchio is a wierd case, IMO. He's hitting .203 with no home runs and 3 RBI's, his hard hit percentage is 28% which means he hits medium or soft 72% of the time, and his ground ball percentage is 49%.
The one skill he seems to have is pulling low breaking balls down the left or right field lines. Of his 13 hits, 7 are doubles. He has 7 doubles in 64 at-bats, which would project to 63 doubles in 576 at-bats if he played every day. As a point of reference, Jose Ramirez had 36 last year and 44 the year before. His career high is 56.
Doubles from a #9 hitter are valuable because if anybody is on base it drives in a run, and if not we have Kwan and Gimenez coming up with a man on second.
Rocchio is at his best with nobody on base; he's hitting .265/.783 with an on-base percentage of .342. Those are very acceptable numbers, and great numbers for a #9 hitter.
But with runners on he wilts under the pressure, hitting .133. With runners on and two out he's 1-for-11 with one walk. He's only 23 so hopefully with more experience he'll learn to relax with runners on base and wait for his pitch. Pitchers know that Kwan, Gimenez, and Jose are up next so they will give him pitches to hit with runners on, especially with two out.
He's also been bad hitting right-handed, going 2-for-18 with one walk. Both hits were doubles, of course. If I were Vogt I would start Arias at short against LHP's; he's 6-for-11!
So hitting left-handed with nobody on base he's been very good. He's hitting a double every 9 at-bats against RHP's. In all other situations he's been awful. He also needs to get better at bunting. If he comes up late in a tie game with a runner on first or second and nobody out he needs to be able to move the runner with the top of the order coming up behind him.