Drop Happ. De La Rosa is a good strikeout pitcher and has a 17-3 combined record from the second half of last season, the postseason, and the start of this season. Following his breakout season, I'd expect him to continue to get better. Happ has the potential to be just as good however you must keep in mind that he has no track record before last season so you can't assume he'll be able to match his numbers from last season. He'd be more of a risk-reward type so you're better off dropping Happ.
@ XDL - Did you even take the time to read the question? The question was if they should DROP Happ or De La Rosa...NOT pick up. And stop making multiple accounts and giving yourself a 'thumbs up' on every one of your answers.