Houston (15-6) at Cincinnati (15-7)

The Houston Astros look to improve upon their best start in 20 years when they send Roy Oswalt to the mound on Friday to face a team he has dominated, the Cincinnati Reds, in the opener of a three-game series.

The Astros (15-6) are off to their best start since 1986, and haven’t won 16 of their first 22 games since 1980.

Oswalt (4-0, 2.48 ERA), also in the midst of the best opening to a season of his six-year career, is 15-0 with a 2.41 ERA in 19 starts against the Reds, giving him the major league record for most wins against an opponent without a loss.

The right-hander is 8-0 with a 2.47 ERA in nine starts at Cincinnati. He went 4-0 with a 2.03 ERA in four starts against the Reds last year.

Oswalt allowed one run in seven innings in his last outing, a 7-2 win over Pittsburgh on Sunday.

The defending NL champions are coming off an 8-5 win over the Los Angeles Dodgers on Wednesday and have won nine of their last 11.

“Whatever happened last year to propel us to the run that we made, it’s really carried over to this year,” Houston’s Chris Burke said. “Guys expect to win ballgames and that’s showing up in the plays we’re making.”

Burke had a career-high three hits with two RBIs in first career start at shortstop Wednesday, while first baseman Lance Berkman went 3-for-4 with a home run and three RBIs.

Burke started in place of Adam Everett, who was hit on the left hand by a pitch Tuesday, and is 11-for-25 this season.

“Now we need to move on from here,” Berkman said. “Cincinnati’s playing well and so are we, so we’ll see what happens.”

Berkman is 26-for-78 (.333) at Great American Ball Park, and his 29 home runs against the Reds are his most against any opponent.

Catcher Brad Ausmus is 15-for-31 (.469) in his last 12 games, and 4-for-5 with four RBIs in his career against the Reds’ Brandon Claussen, Friday’s starter.

Cincinnati (15-7) is off to its best start since 1994. The Reds, winners of four in a row, haven’t been nine games over .500 since June 8, 2004, when they were 34-24.

The Reds lead the NL with 34 home runs and have scored 136 runs, a club record for April. Cincinnati is 6-3 at Great American Ball Park, averaging 7.3 runs in those games.

Cincinnati completed a sweep of Washington on Wednesday, its first of the season.

Adam Dunn went 3-for-5, but hasn’t hit a home run in a season-high nine straight games. The Reds slugger has eight homers on the season.

Cincinnati may activate Ken Griffey Jr. for the Astros series. Griffey, on the disabled list since April 13, is hitting .258 (8-for-31) with two homers this season, and is .160 (4-for-25) in his career against Oswalt.

Claussen (1-2, 6.75 ERA) allowed only six earned runs in his first three starts, but was roughed up by Milwaukee in his last outing Saturday, giving up nine runs and eight hits in three innings. He failed to get an out in the fourth and allowed four homers in the inning, a major league record, as the Reds lost 11-0.

“I am not that bad a pitcher,” Claussen said after the defeat. “I am in the major leagues.”

The left-hander is 3-0 with a 2.98 ERA in his last seven starts at Great American Ball Park, but is 0-3 with a 2.65 ERA in three career starts against the Astros.