The rookie second baseman followed up a stellar major league debut with a two-run single Saturday, helping the Athletics to a 5-2 victory over the New York Yankees.
With ailing shortstop Bobby Crosby (hand) out of the lineup and second baseman Mark Ellis on the disabled list, Rouse was called up Friday from Triple-A Sacramento. He went 3-for-3 with a walk in his first game, then delivered another key hit Saturday.
"When you get to the major leagues you want to make an impression, and he's certainly doing that," A's manager Ken Macha said. "It's been a big boost for us. He scored two runs last night and we won by one."
"I played with Mike in college, at Cal State-Fullerton, and I know what he can do," Saarloos said.
"He was throwing all kinds of stuff -- he's crafty. It's difficult now because he comes at you from so many different angles," Thomas said.
Rouse added a two-run single in the fifth.
"A couple of bad pitches," Mussina said, "and a couple of bad breaks."
Oakland converted a pair of Yankees errors into two unearned runs. New York manager Joe Torre thought Mussina pitched a solid game.
"He wasn't perfect, but he certainly pitched well enough where he could have won the ballgame," Torre said.
New York lost its third straight. The A's (31-31) have won four of five to move back to .500 for the first time since May 22.
Relief pitcher Brad Halsey escaped a jam of his own creation in the seventh, when the Yankees had runners at second and third with one out. But Johnny Damon grounded back to the mound and Derek Jeter struck out, ending the threat.
Halsey got two outs in the eighth, and Chad Gaudin retired Thompson on a bases-loaded grounder to preserve the lead. Huston Street threw a perfect ninth again for his second save in two days and 13th in 16 chances this season.
After Giambi's homer cut Oakland's lead to 2-1, second baseman Robinson Cano bobbled Adam Melhuse's grounder for an error to start the fifth. Marco Scutaro's double put runners at second and third before Rouse slapped a soft single to center.
Thompson's homer made it 4-2 in the fifth, but the A's added an unearned run off reliever Ron Villone in the eighth with the help of an error by Giambi at first base. Dan Johnson blooped an RBI single into short left field.
Mussina allowed four runs -- three earned -- and five hits in six innings. He walked one and struck out seven.
Saarloos gave up two runs and four hits in six innings with three walks and two strikeouts. He earned his first win over the Yankees.
- Jeter started his second consecutive game as the designated hitter after missing three games with a bruised right thumb.
- Thomas also homered in a 6-5 victory Friday night.
- Giambi's homer was his second in two games and third in five games.