That might well be the case. Of his outings since returning from the IL in early June (9 outings including today), three of his four best performances have come when he entered the game with the team trailing (6/9, 6/16, 6/27).Because thru two weeks ago he had pitched 20 times and only gave up runs in 6 outings. And he was nearly perfect all of April. Maybe he only pitches well when the team stinks?
At the very least, he can't be trusted with a lead of any kind for a while.
Edit to add: Looking at his game log, I notice his FIP has consistently been above 4.50 (as high as 5.37) since the beginning of May despite his ERA until recently being below 2.50. His numbers are starting to catch up with his peripherals, which suggests the early season success was an illusion.