HOUSTON (AP) -- Josh Anderson isn't playing like a guy who has 15 games in the major leagues under his belt.
The rookie reached base six times and drove in three runs, and Houston piled up 22 hits to help Brandon Backe win for the first time in more than a year as the Astros routed the Pittsburgh Pirates 15-3 on Sunday.
Anderson, who played 131 games with Triple-A Round Rock before arriving Sept. 1, had five hits and a walk to set a club rookie record for a nine-inning game. Joe Morgan reached base six times as a rookie against Milwaukee on July 8, 1965, in a 12-inning game.
"I'm a little bit surprised," said Anderson, who started his third straight game in center field and raised his batting average to .500. "I had a six-hit game in A-ball in 2004 and I had five hits one other time in the minors.
"It was just one of those days when you feel good, you feel locked in. It's hard to describe. I guess it's like a basketball player hitting several 3s in a row."
It certainly impressed interim manager Cecil Cooper.
"He's an exciting young player," Cooper said. "Hopefully he'll get a chance to continue. It's pretty hard to bench a guy who had five hits. He'll definitely play tomorrow."
Chris Burke had three hits and four RBIs and Ty Wigginton had a home run, double and single as Houston set a season-high for runs to win its second straight. The 22 hits were a club record for a home game.
Backe (1-1), who had Tommy John surgery Sept. 6 of last season, went six innings in his third start of the year and allowed two runs and three hits. He walked two and struck out two.
The right-hander, who started out as an infielder in the Devil Rays organization, also doubled, singled and scored twice.
Paul Maholm (10-15) wasn't nearly as good, lasting just 2 2/3 innings and giving up 10 runs and 11 hits. Maholm had beaten the Astros twice this season and allowed only two runs in 15 2/3 innings in those games. He's 3-3 against them in his career.
"I felt good, but for some reason I threw everything belt high and this is the wrong park to try that one in," Maholm said. "I make a perfect pitch to the first hitter and he gets on. Then all of the sudden, I start trying to throw hard for some reason."
Houston scored five in the first on Anderson's RBI double, a run-scoring single by Mark Loretta and Ransom's homer.
After Jack Wilson hit his 12th homer of the season in the second, Anderson's RBI single in the bottom half of the inning made it 6-1.
The Astros added five more and chased Maholm in the third inning. J.R. Towles had an RBI single and Burke a two-run single. Reliever Juan Perez then entered and gave up three straight singles, the last a two-run hit by Carlos Lee.
"Paul was rusty," Pittsburgh manager Jim Tracy said. "He left a lot of balls in the middle of the plate. I just don't know what would have happened if he could have gotten through that first inning.
"That at-bat to Ransom in the first I thought was huge. There were two on and two out and that was the big one today. He gets through that one and who knows what he does the rest of the day."
Jason Bay hit his 21st home run in the fourth.
Wigginton led off the fourth with his 22nd home run, his sixth since coming to the Astros in a trade July 28. It was his third home run in two days.
Burke hit a two-run homer in the eighth. It was his sixth home run of the year.
The previous home mark for hits was 21 set July 11, 1970, in the Astrodome against the Giants. ... The homer was Ransom's first in the majors since Aug. 14, 2004, when he played for the Giants against the Phillies. ... Wilson's double in the fourth was his 1,000th career hit. ... Brad Ausmus entered in the eighth inning to play third for the second time in his career. The first time the catcher played that position was Oct. 1, 2000, against Minnesota.