"He was laboring," manager Ron Washington said. "He was struggling from pitch one. In [almost] every inning, he was in trouble. That inning we got to the middle of their order, and I wanted to shut the inning down."
Washington, wanting to protect a two-run lead, brought in Roman Mendez to stop the threat. But Mendez gave up an infield single to Dexter Fowler and then a grand slam to Jason Castro that gave the Astros a 4-2 victory at Minute Maid Park.
Mendez, who ended up with his first Major League loss, had thrown seven straight scoreless innings before Castro hit the grand slam.
Tepesch had also been on a roll of late, with a 3.46 ERA in four August starts, but he couldn't finish the month with another quality start.
"Long innings, no clean innings," Tepesch said. "A lot of pitches per innings. It's tough to pitch deep into the game throwing so many pitches."
"He wasn't able to get his breaking ball over," Washington said. "His sinker wasn't there, either. He just didn't have it. He just couldn't get anything where he wanted it."
The Astros have now won nine of 13 against the Rangers after starter Collin McHugh allowed two runs in seven innings. He allowed eight hits but did not walk a batter and struck out six.
"The Texas Rangers handed it to us last year," Astros manager Bo Porter said. "Man to a man, we all came out with the thought process this year [that] we want to reverse our fortunes against them, and we've played some of our best baseball against them this year."
The Rangers went 1-for-8 with runners in scoring position, missing chances to build more than a two-run lead early.
Texas started the game with singles by Leonys Martin and Elvis Andrus that put runners on the corners but only got one run, when Mike Carp grounded into a double play. They loaded the bases in the second on singles by Robinson Chirinos, Martin and Andrus but again scored only one run.
Carp sent home the run with a sacrifice fly, and the other runners moved up to second and third on left fielder Marc Krauss' errant throw to the plate, but McHugh struck out Adrian Beltre and Jim Adduci to end the threat.
"We had some situations, but [McHugh] made some good pitches," Andrus said. "When you face a guy for the first time, sometimes you have the advantage, and sometimes you don't. He just made good pitches. The next time we'll know him better."
Tepesch started the fifth by getting Marwin Gonzalez on a fly to center, but Jose Altuve singled and Chris Carter walked. That's when Washington went with Mendez; Tepesch didn't argue.
"You want to go deep in the game, but that's not my call," Tepesch said. "I respect whatever call they make."
Mendez first had to face Fowler, who beat out a slow grounder to Beltre. That brought up Castro, who entered the game in an 0-for-20 slump before delivering a single and a walk in his first two plate appearances. Mendez got behind, 2-0, before having to come with the fastball, and Castro crushed it into the right-field seats.
"Just trying to be as short as I can and trying to put the ball in play," Castro said. "I was really just looking to get something I could drive in the air so that worst-case scenario, we had a sac fly, and luckily enough, I got the barrel on it and I was able to put a short swing on it, and it was able to go out."