Ohlendorf's mound opponent, conversely, will be left-hander Wandy Rodriguez, the most enduring constant on the Astros staff during the time when they went from National League champions and World Series participants in 2005 to 106 losses last season.
Ohlendord became San Diego's 12th different starting pitcher this season when he started June 16 against the A's.
With six starters on the disabled list, most recently Anthony Bass, who headed there Saturday, the Padres turned to Ohlendorf, who was mined from the Red Sox's system, where he pitched for Triple-A Pawtucket earlier this season.
The Princeton graduate didn't allow a hit until the fourth inning against Oakland, but weakened and ended up throwing 85 pitches in 4 2/3 innings, yielding three runs.
In three appearances for the Padres, he is 1-0 with a 4.50 ERA.
Ohlendorf had taken a calculated risk when he opted out of his Minor League contract with the Red Sox with the hope the Padres would sign him.
San Diego had shown interest in him before Spring Training, but opted to sign right-hander Jeff Suppan.
Suppan lasted just six starts with the Padres, and when injuries to the starting pitchers began mounting, Ohlendorf's gamble paid off.
Whether Ohlendorf will continue as a starter remains to be determined, but he's happy to be in the Majors and will do what it takes to stay.
"I'm happy to pitch in whatever role they need me," he said.
"He's been around the block, he knows what he's doing," manager Bud Black said.
For the Astros, Rodriguez is 6-5 with a 3.29 ERA in 15 starts. Since 2005, the 33-year-old lefty had yearly start totals of 22, 24, 31, 25, 33, 32 and 30.
During his career, he has started 212 games and is 79-80 with a 4.01 ERA.
Rodriguez took a tough-luck 2-0 loss to the Royals in his last outing Tuesday.
He pitched seven innings and allowed six hits and both runs as the Astros were shut down by Royals right-hander Luke Hochevar.
Houston manager Brad Mills thought Rodriguez had trouble against the Royals finding a groove and settling into the kind of rhythm that he's in when he's on his game.
"We'd like him to get in that rhythm right away," Mills said.
Padres: Alonso hurting
First baseman Yonder Alonso, who is second among rookies with 17 doubles and fourth with 64 hits, will not play Monday due to a sore left knee that Black described as "cranky."
Alonso got an injection to ease the soreness Saturday night, and is expected back Tuesday, Black said.
Jesus Guzman, normally an outfielder/pinch-hitter, will start in his place against the lefty Rodriguez, the manager said.
Astros: Lee getting hot
First baseman Carlos Lee had two more hits in Sunday's 7-1 victory over the Indians and was 6-for-12 in the final three games of the series with four RBIs.
He has his batting average up to .303.
The Astros and Padres haven't played each other this season, but they will get together often in the next few weeks.
In addition to the four games at Minute Maid this week, they will play four in San Diego from July 16-19.