Showalter improved to 1,000-958 in 14 seasons with the Yankees, Arizona, Texas and Baltimore.
"I'm very appreciative of the players making me feel really young tonight, even though I'm an old goat," Showalter said.
He joined Dusty Baker, Bruce Bochy, Davey Johnson, Jim Leyland, Mike Scioscia and Bobby Valentine among active managers in the 1,000-win club.
In other games *
At Toronto, Brett Lawrie hit a walkoff home run in the ninth inning and the Blue Jays beat the Texas Rangers, 8-7.
* At Chicago, Gordon Beckham went 3-for-4 with two RBI as the White Sox beat the Cleveland Indians. 7-2.
* At Detroit, Austin Jackson had four hits to lead the Tigers past the Kansas City Royals, 9-3.
* At St. Petersburg, Fla., Matt Joyce had two of Tampa Bay's three hits, including a solo homer and RBI triple, to help the Tampa Bay Rays beat the Seattle Mariners, 3-1.
* At Boston, Jemile Weeks drove in a pair of runs and scored twice as the Oakland Athletics beat the Red Sox, 5-3.
* At Anaheim, Torii Hunter had a homer and RBI single and Jerome Williams (2-1) threw a three-hitter as the Angels beat the Minnesota Twins, 4-0.
Yankees pitcher Andy Pettitte testified during Roger Clemens' perjury retrial that his onetime teammate told him he took human growth hormone.
"Roger had mentioned to me that he had taken HGH," Pettitte testified. "And that it could help with recovery, and that's really all I remember about the conversation."
Pettitte went on acknowledge that the words were said in passing during an intense workout.
It's a conversation that Clemens has famously claimed that Pettitte "misremembers."
Clemens is charged with lying when he told Congress in 2008 he never used steroids or HGH.
The government interrupted testimony from the trial's first witness to call Pettitte just before noon, and he could return to the stand Wednesday.
* Tampa Bay placed Evan Longoria on the 15-day disabled list with a partially torn left hamstring. He was injured Monday while running to second base on an attempted steal. He slid into the bag and remained on the ground for a moment before climbing to his feet and walking to the dugout without assistance.
* The Indains purchased the contract of Johnny Damon and intend to start him in the outfield Wednesday. The 38-year-old Damon, now in his 18th major league season, needs 277 hits to reach 3,000. He signed a minor league deal with the Indians on April 17 and has spent the last few weeks getting ready at the club's facility in Goodyear, Ariz.
* OutfielderNolan Reimold will miss the final two games of the Orioles' series against the New York Yankees because of a bulging disk in his back.