In that start on June 26, Lyles went 6 1/3 innings, giving up one run on six hits. He struck out four and walked four with 103 pitches.
The 21-year-old followed up that start with a rough one on July 2, giving up seven runs in four innings, before having another solid performance on July 8, when he went seven innings and allowed two runs.
"The last couple of outings have been all right, and I just want to continue to keep doing that and continue to work on my curveball," Lyles said. "It's coming along pretty nice. I feel good about it and I feel like I'm going to have a good second half."
Earlier this season, Lyles began gripping and throwing the curveball in the same fashion of left-handed teammate Wandy Rodriguez, who is considered to have one of the best curveballs in the big leagues.
The Padres' starter, Austin-native Ross Ohlendorf, will try to finally find some success against the Astros.
He allowed five runs in 3 2/3 innings against Houston on June 25 and is 0-6 in his career against the Astros. The six losses are his most against any team.
Ohlendorf has been used as both a starter and long reliever so far in 2012, making two starts and four appearances out of the bullpen and posting a 7.41 ERA.
A spot in the rotation may be on the line. Left-hander Eric Stults is making a rehabilitation start at Triple-A Tucson Tuesday night and could take Ohlendorf's slot in the rotation if the right-hander pitches poorly against the Astros.
Padres: Vincent back in the bullpen
Reliever Nick Vincent is back with the Major League club for the third time this season after being recalled from Triple-A Tucson on Monday.
"We feel as though the way Nick is throwing the ball now. ... He's just a little bit more consistent than some of the other guys that have come up," Padres manager Bud Black said. "We like how he's throwing the ball, we like his stuff. ... He does a lot of things well."
The Padres optioned reliever Miles Mikolas to Tucson before Monday's game.
After throwing 1 2/3 hitless innings Monday, Vincent has a 5.68 ERA in 6 1/3 innings. He has struck out seven batters and walked three.
Astros: Wallace expected to be with club soon
When Carlos Lee was traded to the Marlins on July 4, most expected Minor Leaguer Brett Wallace to replace him at first base for the rest of the season. Wallace remains in Triple-A Oklahoma City 14 days later, but general manager Jeff Luhnow said the first baseman will be in the Majors again soon.
"Brett will spend the vast majority of the remainder of the season in Houston," Luhnow said. "Right now, there are a lot of moving parts between injuries and guys coming back from injuries and other things that may or may not occur the rest of this month. We haven't made the decision to do it right now, but I would suspect Brett will spend the bulk of the season in Houston."
Wallace hit .333 in 11 games with the Astros earlier this year. He is batting .286 with 13 homers and 46 RBIs for Oklahoma City.
The Astros are currently platooning Scott Moore and Matt Downs at first base. Moore went 1-for-2 with two sacrifice flies Monday.
Houston drew nine walks on Monday, tying a season high. The Astros also walked nine times against the Padres on June 25 at Minute Maid Park.
On Monday, the Astros won their first game away from Minute Maid Park since June 14 at San Francisco. They had lost 13 consecutive road games.
The Astros and Padres have two of the three youngest rosters in the National League. The Astros' average age is 27.3 and the Padres' average age is 28.5.