Harrell, though, is coming off his worst outing since the All-Star break and the Astros are seeking to bounce back from their first loss to the Mets this year in Sunday's series finale.
Houston (40-87) is on pace to surpass its franchise-worst 106 losses from 2011 and needs to win at least 16 of its final 35 games to avoid that dubious feat. That doesn't appear likely given that it has won only eight of its last 52.
The Astros do have one more game against the Mets (58-69), a club they had beaten four straight times before a 3-1 defeat Saturday. Houston doesn't have a winning record against any other NL team in 2012.
Justin Turner hit his first home run of the season while helping New York snap a six-game skid, but he could be out of the lineup Sunday after starting consecutive games in place of the resting Daniel Murphy.
Harrell (10-9, 4.04 ERA) will try to help Houston rebound from that loss while regaining the form he showed in his first seven second-half starts. The right-hander was 3-2 with a 2.06 ERA over those games, allowing two runs or fewer in each, but the Missouri native gave up six over five innings of a 7-0 loss in St. Louis on Tuesday.
"I felt like I let everybody down," Harrell told the Astros' official website. "I wasn't at my best. I'm very disappointed, frustrated and disappointed - all of those words come into play."
Harrell will make his first start against the Mets and Jeremy Hefner (2-5, 5.11) will make his first versus the Astros in his first game since his wife Sarah gave birth to a girl named Jaylee on Wednesday.
Hefner will try to follow that event with an improved performance. The right-hander rejoined the Mets' rotation last Sunday and gave up five runs - including two homers - in five innings of a 5-2 loss at Washington in his first start in two weeks.
"Sometimes you get away with mistakes, and sometimes you don't, and today, I didn't get away with any," Hefner said.
With Houston heading to the AL next season, this game will mark the teams' final meeting as NL opponents. Among the highlights in the rivalry was a six-game NL championship series in 1986 that the Mets won en route to their most recent World Series title.