Both pitchers, however, have had some success against the other's club, and they'll oppose each other Friday afternoon in the opener of a three-game set at Wrigley Field.Maholm (4-6, 5.38 ERA) is 11-6 with a 3.31 ERA in 20 career outings against the Astros (32-44), his highest victory total against any opponent.He's 0-4 with a 6.43 ERA during his winless run, though, and Houston has won a respectable 11 of 21 games against left-handed starters.Maholm gave up a season-high seven runs over 3 1/3 innings last Saturday in his shortest outing of 2012, a 10-5 loss at Arizona. He fared better at the plate with a two-run homer -- his second hit of the year.The southpaw could be poised to cool off Astros third baseman Chris Johnson, who is 1 for 12 against him.Johnson is hitting .371 in his last nine games for Houston (26-49), which is making its first trip of the season to Wrigley. Chicago is also where the Astros will end their stint as an NL club Oct. 1-3, before moving to the AL for 2013.Norris (5-4, 4.81) is 0-3 with a 10.91 ERA in four starts since beating the Cubs on May 21 with seven scoreless innings in an 8-4 home victory. He will be activated off the disabled list after being out since June 12 with a sprained right knee.Norris allowed two runs and struck out seven over five innings of a rehab start Saturday for Triple-A Oklahoma City."It's out of my head now," Norris told the Astros' official website. "I feel pretty good, and I'm excited to get back out there when I can."The right-hander's lowest career ERA against any opponent is his 1.89 mark versus the Cubs. He's 3-2 with a 1.78 ERA in five starts against them.Norris will get his first look at first baseman Anthony Rizzo, who went 3 for 8 this week in his first two games with the Cubs after being called up Tuesday from Triple-A Iowa. Manager Dale Sveum said he will continue to use Rizzo in the No. 3 slot.The Cubs fell 17-1 on Wednesday to the Mets, as their bullpen allowed a season-high eight runs over 4 2/3 innings."The way our bullpen is we need a day off," Sveum said. "Guys have been pitching a lot."Houston lost for the second time in six games Thursday when closer Brett Myers surrendered six runs -- five unearned -- in the ninth inning as an error by Johnson proved to be crucial in a 7-3 defeat to San Diego."I don't blame it on anything except me," Myers said. "It's my job to shut the inning down and pitch around mistakes."Astros manager Brad Mills said second baseman Jose Altuve, out of the lineup for four straight games with a strained right hamstring, will not return until Sunday at the earliest.Houston starters posted a 0.90 ERA in a three-game home sweep of Chicago from May 21-23, the only previous series this season between the NL Central's worst teams.