"He was efficient with his pitches and was on the attack and used his changeup," Porter said. "Even a couple of times when he was behind in the count, he was confident using his changeup."
Clemens (4-5), making his first start in nearly two weeks because of a blister, allowed two runs and six hits in a career-high seven innings in only his third Major League start. He was scratched from his previous start last Sunday.
"I'm happy with some of it and there was some pitch selection that has got to get better," Clemens said. "I don't know how much you guys were watching, but there were some at-bats there where pitch selection was wrong. This game comes down to two things: executing your pitches and choosing the right pitch in the right situation. I just want to continue to get better at those things."
Angels starter Jerome Williams (8-10) held the Astros to one run through seven innings -- coming on a home run by Marc Krauss in the second inning -- then watched closer Ernesto Frieri pick up a six-out save by working the eighth and ninth innings.
"This game doesn't get easy," Frieri said. "When guys get to know you and get to know what kind of pitches you throw, it's tough. That's why you keep needing to make adjustments, improving yourself and working hard."
The Astros, who are hitting .351 with runners in scoring position in September, were 0-for-4 in those situations Sunday, marking the first time in 14 games this month they didn't manage a hit with runners in scoring position.
Two of those at-bats came in the eighth after Brandon Barnes singled to start the inning and Jonathan Villar drew a walk against Dane De La Rosa to put the go-ahead run on base. The Angels summoned Frieri.
Jose Altuve, who entered Sunday leading the Majors in batting average and hits in September, put down a sacrifice bunt to push the runners to second and third with one out. Frieri stuck out Trevor Crowe and Brett Wallace swinging to strand the runners.
"The one at-bat that was really frustrating was against Frieri," Crowe said. "I felt like I got two pitches to hit. You have to give some credit to him because he's got good stuff. Those are the ones that are frustrating as players. Sometimes you are going to get out, but you don't want to make outs.
"I felt like on that particular at-bat, I made an out. He obviously has some good stuff. I had never seen him before. He's got some life on his fastball. That's the at-bat I'd really like to have back."
Porter said the decision to sacrifice Altuve was easy.
"You force them to play the infield in, believing that you're going to get contact from Trevor Crowe, who is swinging a hot bat," he said. "With contact, you're actually thinking to yourself, 'If he hits a base hit here, we actually take the lead.' You're not only putting the tying run 90 feet away, you're also putting the go-ahead run at second base."
Matt Dominguez led off the ninth with a single against Frieri following a 12-pitch at-bat, but the closer struck out Chris Carter, got Krauss to pop out, then struck out pinch-hitter Brandon Laird for his first career two-inning save.
"We had our opportunities and we just weren't able to capitalize," Porter said.
The Angels rallied after Mike Trout drew a two-out walk in the first inning. He stole second base and scored on a triple by Josh Hamilton, who sent a long fly ball onto Tal's Hill in center field that just eluded Brandon Barnes. The ball traveled more than 420 feet.
"You never know with Barnes," Clemens said. "Barnes seems to catch everything. Sometimes when you get behind in counts, you turn around and give Barnes a little nod and you see if he can run them down. Ninety-nine percent of the time, he runs them down. That guy's been tremendous out there for us all year and we don't expect anything different out of him."
Krauss' homer in the second inning -- the fourth of his career -- tied the game at 1.
Clemens (4-5) retired 10 of the next 11 batters he faced before Erick Aybar and Hank Conger led off the fifth with consecutive singles, putting runners on the corners with no outs. Andrew Romine scored Aybar with a sacrifice fly to left field for a 2-1 lead for the Angels.
"When I got called up, I wanted to show them I was here to compete, and I went after guys aggressively with my fastball and it's starting to burn me," Clemens said. "It feels like I'm giving up a home run every inning. I really want to focus on my execution and my pitch selection, and not be so aggressive anymore and not challenge too many guys. This is the AL. This is goon ball. All across this league, guys can hit it a mile."