This is the kind of tactical question that is difficult to evaluate mid-season. Clearly, Cora wanted to preserve a gradual ramp-up of the SP arms through April, especially given the weird COVID/lockout disruptions of the seasonal rhythms of the last few years. The idea seemed to be that this would help our thin rotation go the distance until reinforcements could arrive from the IL and the minors — Kutter Crawford was dealing yesterday, huh?
And because of this, we leaned pretty hard on the bullpen in April, and, well, they couldn't carry that burden and it cost us a few games. The slow start from the offense meant that every slipup and bad outing was magnified, because we were in a ton of close games; thus our bullpen turned okay statistics (15/30 in bullpen bWAR) into the league lead in blown saves. If Diekman allows a few walks in the seventh inning of a 9-2 game, no one cares. If he does it in a 2-2 game... But I'd note that the pen has been pretty great lately, even notwithstanding Robles' meltdown in Seattle. The starters going deeper has really helped a few of these guys regain their footing.
So that's the cost of Cora's strategy in conjunction with the April offense. But if it means that we are in a strong position pitching-wise for one of these three game wildcard series we have now, it will have paid off. If we don't make the playoffs, or it fails to keep enough pitchers healthy — Whitlock and Eovaldi are on the IL, but at least it isn't for arm-related issues...; but Sale threw 96 off a mound in Fort Myers today — that will be the time to second guess him IMO. But where we stand now, with the eighth-best rotation, third-best offense since May 1, and a middling bullpen that we have the resources to improve, makes me feel like it could work.