HOUSTON — Scott Feldman led the American League with a 1.33 ERA in August.
The start of September didn't go nearly as well for the Houston starter, who left in the third inning of Tuesday night's 7-5 loss to the Seattle Mariners with discomfort in his right shoulder.
He walked five and gave up three hits and three runs in 2 2-3 innings before his early exit.
Feldman walked two straight batters before grimacing after a pitch to Mark Trumbo that resulted in a fly out for the second out of the third inning. Trainers visited with him briefly on the mound before he left the game and was replaced by Vince Velasquez.
"It felt worse and worse," he said. "It felt tight at the beginning of the game, but (then) it started feeling to where it was actually starting to hurt. You got to try to know the difference between tightness and putting yourself and the team in a bad position. Once I started hurting, I don't want to go out there and tear my shoulder."
He'll have an MRI on Wednesday.
"It was just one of those nights where it was going to be a battle," Feldman said. "I didn't have my best stuff or command or anything. I was trying to battle through it. Then unfortunately the shoulder started hurting."
Logan Morrison's tiebreaking two-run pinch-hit homer in the eighth inning led Seattle to the victory.
The game was tied 5-5 when Morrison hit the third pinch-hit homer of his career, sending a pitch from Pat Neshek (3-4) into the seats in right field.
"I'm trying to get a strike over, but I'm trying to hit my spot," Neshek said. "I missed a little bit in, and he did what he's supposed to do, took a big hack and pulled it really well."
Franklin Gutierrez hit a solo homer in the second, and Trumbo, who homered twice on Monday, added a two-run shot off the train beyond Houston's left-center field wall to give Seattle a 5-3 lead in the fifth.
Jose Altuve hit an RBI single with two outs in the sixth to get Houston within one run. The Astros tied it up when Jake Marisnick scored from third on an error by catcher John Hicks when he tried to pick off Altuve at second base.
Manager A.J. Hinch liked the way the Astros fought back even though they came up short in the end.
"Obviously the character of this team is really good," he said. "We've done this before where we've fallen behind and come back and played."
Logan Kensing (1-0) pitched a scoreless seventh for his first win since 2009 and Tom Wilhelmsen threw a perfect ninth for his seventh save.
Marisnick had a solo shot in the fourth for the Astros, who remain in first place in the AL West.
Mariners starter Roenis Elias allowed five hits and four runs with four walks in 5 1-3 innings.
Gutierrez led off the second with his 11th homer to put Seattle up 1-0. Seth Smith followed with a triple before the Mariners added another run after Feldman walked three consecutive batters with two outs in the inning.
Max Stassi cut the lead to 2-1 with a two-out RBI single in the second inning.
After replacing Feldman, Velasquez promptly allowed a single to Brad Miller that made it 3-1.
Houston got within 3-2 on a sacrifice fly by Carlos Gomez in the third, and Marisnick's homer tied it in the fourth.
Carlos Correa snagged Robinson Cano's line drive with a diving effort for the first out of the fifth. Trumbo's 20th homer came with two outs in the inning.
Astros: OF George Springer (broken right wrist) will play two more games of a rehabilitation assignment in Double-A Corpus Christi before the Astros decide what's next for him. ... Reliever Tony Sipp has been bothered by an unspecified back injury for about a week and won't be available in this series.
Seattle's Taijuan Walker (10-7, 4.53) opposes Scott Kazmir (7-9, 2.45) when the series wraps up on Wednesday. Walker is 3-0 with a 3.12 ERA in his last six starts, which included a one-hitter against Minnesota on July 31.