The Phillies bullpen has been among the best in baseball since the All-Star break. In the second half, they rank third in fWAR (1.5), ninth in ERA (3.45), and fourth in fielding-independent pitching (3.59). You would expect rookie Seranthony Dominguez to be at the center of that, but he has struggled in the second half.
In 11 appearances since the All-Star break, Dominguez has actually been below-replacement level with the second-lowest fWAR (-0.2) among the team’s relievers during this time. He has a 4.66 ERA and 5.64 FIP, walking seven batters and allowing eight hits in 9.