Astros setup man Ken Giles came out in the eighth to protect a two-run lead but got into immediate trouble and retired just one batter as the Athletics scored five runs in the last two innings to race past the Astros, 7-4, on Friday night.
Carlos Gomez was thrown out trying to stretch a double into a triple leading off the ninth and things unraveled in hurry.
"It feels like something always happens that we can't finish these games," Fiers said. "Giles' stuff is too good for him to continue scuffling. We trust in him. He'll come out in the eighth the next time and get the job done. We've seen it in the past."
Fiers did his job to give the bullpen some rest. He completed seven innings, leaving the game with a 4-2 lead. He struck out five and didn't walk a batter.
"It was big for me and big for the team," Fiers said. "This starting staff knows it can go deep into games."
Fiers had all of his pitches working and even Coco Crisp's two-run homer in the second inning was a decent pitch.
"He just got on top of it and got it out," Fiers said. "We had a good gameplan and I didn't have to shake off Kratz much."
Fiers threw 74 of his 104 pitches for strikes.
Gattis, who has hit in a season-high four straight games, drove in the Astros' first two runs.
"I've been working with [hitting coach Dave Hudgens] on treating every at-bat the same," Gattis said. "Before I would go after RBIs. It's been better the last couple of games."
Astros manager A.J. Hinch said Gattis has been getting into hitters counts, where he can cover more of the plate and be aggressive.
"When you're behind in the count, you're defensive and you don't cover as much of the plate," Hinch said. "When he gets into an aggressive mindset, he's much better."
On a night when spark-plug Jose Altuve ended a 19-game streak of reaching base safely, the Astros were still in a position to win the game. Instead, Houston lost for the first time in seven games when leading after seven innings.
Gomez collected two hits, showing there's no hangover from Wednesday's game in Seattle when he was forced to leave the game after getting hit by a pitch on his right hand.
George Springer went 1-for-3 and has reached base safely in 14 straight.
Rick Eymer is a contributor for MLB.com and covered the Astros on Friday.