Stammen allowed four runs on four hits in Game 1 of Thursday's doubleheader against the Mariners. He did not record an out.
Stammen came on to pitch the top of the seventh with the game tied at 3-3. He allowed four singles and a hit-by-pitch without getting an out. He left the game with the Mariners leading 6-3 and was charged with one more run when Austin Nola extended Seattle's lead with a sacrifice fly. Luckily for the right-hander, the Padres let him off the hook by rallying for four seven runs in the bottom half of the inning. Stammen's ERA jumped to 7.90 on the campaign, although it's worth noting that 11 of the 12 earned runs he's allowed came in three bad outings.