Fantasy Question? Tabata? Narveson?

Okay, I need some input from some knowledgeable peeps. Now my Head-to-Head League has decided to set a max of 2 acquisitions per week. I like and hate this at the same time. Requires more strategy but it's a little maddening. Anyway, I drafted Ryan Raburn at second but he is not going to be getting as much playing time thanks to Brennan Boesch so I will be using my first pickup for Howie Kendrick, (who was actually dropped by another team?) and I am torn on my next choice. Chris Narveson has had himself a nice start to the season. However, will he continue his dominance? He will drop back to number 5 starter once Grienke comes back. I like the offense he can get in Milwaukee but I doubt his ability to be this dominant consistently. My other choice is the young Pirate Jose Tabata. This kid is scorching right now with his bat, even managing to belt a couple homers. Pretty good for a 10 HR a year guy. He has also snagged himself 5 bases so far. My only issue is the Pittsburgh Pirates. They seem like a scrappy young team and with Tabata leading off he should score a ton of runs and steal a bunch of bases. I have Rajai Davis currently but he has twisted his ankle twice and is too much of an injury risk right now. I don't really need Narveson but it would strentghen my roation even more. I love strong pitching so this is why it is a hard decision for me. SO which player has the more upside and you think will continue their hot season?