HOUSTON(AP) Russ Ortiz is unhappy with his role.

That's just fine with the Astros, as long as he keeps pitching the way he did Sunday in Houston's 6-4 win over the Pittsburgh Pirates .

Felipe Paulino , who took Ortiz's spot in the rotation earlier this season, strained his right groin in the second inning and left the game. Ortiz came on in relief and tossed 4 1-3 scoreless innings. He gave up four hits and a walk, striking out three.

''Ortiz did a really good job,'' Houston manager Cecil Cooper said. ''Russ has pitched much better than he did as a starter. He's more consistent in the strike zone.

''He wasn't happy when we put him in the bullpen and he probably still isn't happy. But we've talked with him several times and he knows what role we need him to play.''

Not that Ortiz is accepting that role. In nine relief appearances since the demotion, he has a 2.50 ERA. He ran his scoreless streak Sunday to 12 1-3 innings, the longest by an Astros pitcher this season.

Does Ortiz think he has pitched well enough to start again?

''That's a question for them,'' he said. ''Of course I want to start. That's what I love to do.

''But I've been told my role is long relief. Those things are not up to me. All I can do is work hard and do my best,'' he added. ''It's nice to have a good outing and make a case for myself. I hope I can just give Cooper more confidence in me every time I go out there.''

Matt Kata scored from second base on Miguel Tejada 's infield single, snapping a seventh-inning tie, and the Astros held on from there.

Pirates shortstop Ramon Vazquez went to the turf to field Tejada's grounder, fumbled the ball and tried to get it to second baseman Freddy Sanchez for an inning-ending force. But they couldn't connect and Kata never stopped running, putting Houston ahead 4-3.

''There were two outs, so why stop?'' Tejada said. ''Some guys might stop, but you have to try and make something happen in that situation.''

The Pirates thought it was a good play by Kata.

''It was close,'' Vazquez said of the play at second. ''I was falling down, but that was the best chance I thought we had of getting the out.''

Steven Jackson (1-1) took the loss, allowing three runs, three hits and two walks in 1 1-3 innings.

''That was a really heads-up play by (Kata) and all you can really do is tip your cap to him,'' Jackson said.

Humberto Quintero , who went 3 for 4 with two RBIs, had an RBI single and Jason Michaels added a run-scoring double in the eighth to make it 6-3 .

Chris Sampson ran his shutout streak against the Pirates to 24 innings with a perfect eighth. LaTroy Hawkins allowed a run in the ninth before getting his eighth save in 10 tries.

Jeff Fulchino (1-1) pitched a scoreless inning for his first major league win.

Pittsburgh rookie Andrew McCutchen had three hits and an RBI. The Pirates are a half-game in front of last-place Houston in the NL Central.

Pirates starter Ian Snell pitched six innings and allowed three runs on eight hits and a walk. He struck out three.

''I thought he threw really well today,'' manager John Russell said. ''He got ahead of hitters and made (the Astros) put the ball in play. His command was there and that really helps him set up his off-speed stuff.''

Jason Jaramillo 's RBI double gave Pittsburgh a 1-0 lead in the second. The Astros tied it in the bottom half on Jeff Keppinger 's RBI single.

In the fifth, Quintero's double drove in Keppinger for a 2-1 Astros lead. Carlos Lee made it 3-1 with an RBI single in the sixth.

Tim Byrdak relieved Ortiz to start the seventh and loaded the bases without getting an out. Fulchino got McCutchen on an RBI groundout. Nyjer Morgan 's RBI single tied it 3-all.

Morgan also had a sacrifice fly in the ninth.

Notes: Pirates SS Jack Wilson was out of the lineup with a sore shoulder. He is day to day. ... Astros relievers Geoff Geary and Jose Valverde each threw two simulated innings before the game. Valverde, on the disabled list with a right calf strain, planned to throw only one inning but felt so good, he went two. He is slated to pitch Tuesday and Wednesday in a minor league rehab assignment at Double-A Corpus Christi and likely will be activated for the Arizona series that starts Friday. Cooper said Geary (right biceps tendinitis) also might be ready by Friday. ... 2B Kaz Matsui (strained left hamstring) ran and took grounders again, and the Astros are considering sending him on a rehab assignment this week.