He needs to be better for sure. And this was his worst start since the first one - six runs allowed in each of those. 3, 1, 2 and 3 in the others. This was also his first loss (the team's second, after the extra-innings one with the Mets). The team can afford to have him eat these innings as a serviceable #5 right now. Wasn't all on him yesterday (defense, manager, offense).
Still falls under the category of "good problem to have," including that the bullpen, while not as dominant in May, can afford to give up that spot to Turnbull.
But if I were them I'd figure out a way to get him to take an assignment to AAA - fully guarantee his current deal (which includes incentives he can't reach so long as he doesn't start), set a July start date for the six-man rotation and get him stretched back out/on routine. They could also quietly hint that he'd be traded to another contender at the deadline (that would be risky depth-wise, but in the long run you have to wonder if there is a spot for even one of Turnbull or Walker in the post-season, let alone both).