Manoah and sometimes Kikuchi. Gausman has had 3 implosions I think, otherwise he's been the best pitcher in baseball.
Bullpen despite the depth and despite how some on here praised it as an elite pen, isn't one still. Romano is rock solid, Swanson has done a formidable job, Pearson looks like he has found a new home down in the pen, Mayza has been great and Richards is having a terrific season. The rest have been extremely disappointing (Bass, Cimber, Garcia, Pop). They've been dumpster fires when they're supposed to be arms you could rely on in the 6th/7th inning's. Bass actually looked like he was starting to turn things around, but won't go there. Otherwise, if they were posting solid numbers, this pen would look completely different.
Offensively, it's not the main problem but still is an issue. This team has underachieved offensively power wise and are also inconsistent on a day-to-day basis. Like I said before, you might be only looking at one 30 HR bat in this lineup which is Bo, who typically shouldn't be your team HR leader.