Girardi didn't seem interested in shedding any light on the first-inning fracas that had Showalter angry and emptied both dugouts.
Tillman took a three-hitter into the eighth inning and the Orioles beat the Yankees 4-2 on Monday night in the opener of a four-game series with ramifications in the AL wild card race.
"They are all big this time of year, and I take the approach every game I'm pitching," said Tillman (16-5), who became the Orioles' first 16-game winner since Mike Mussina won 18 in 1999. "You only get to go out there once every fifth day, so for me they are all big."
With the victory, the Orioles remained tied with Cleveland and moved within 1½ games of idle Tampa Bay for the second AL wild card. The Yankees fell three games behind the Rays.
Tillman allowed two runs and four hits in seven-plus innings. He walked none and struck out nine, matching his career high.
"I was able to get in sync and kind of felt my way through the first couple innings," Tillman said. "I found it later in the game and I think (catcher Matt Wieters) gets a lot of the credit for that. He made some calls deep in the counts. And it was fun."
But his performance almost became an afterthought after the skirmish between Showalter and Girardi.
Following the game, Showalter patiently answered inquiries about the clash before asking reporters to change their line of questioning.
"Guys, we had a great pitched game tonight," he said. "I understand you've got to ask the questions and everything. I'd rather have the focus be on Chris Tillman, some of the things we did on the field. ... I know how drama usually plays this time of the year. I'm just glad we're playing games that mean this much to everybody, including our fans."
Both dugouts emptied briefly after the first inning, when Showalter angrily exchanged words with Girardi after the Yankees manager yelled at Baltimore third base coach Bobby Dickerson, accusing him of stealing signs. Showalter had to be restrained by home plate umpire Ed Hickox as he charged onto the field.
Girardi refused to go into specifics about what set him off, saying only, "The one thing that I've done, the whole time that I'm here, and everywhere I've been, is I'm going to protect our players at all lengths. That's what I'm going to do, and there was something that I saw and I'm just going to leave it at that."
Dickerson, who said he had never been berated like that by an opposing manager, said he heard Girardi chirping from the dugout from the start of bottom of the first. Girardi had moved from the end of the bench close to the plate to the end of the dugout nearest third base by the time the inning had ended.
"Immediately, like right when I got to third base," Dickerson said. "I didn't hear him at first. I heard something and as I looked at the dugout, he was right there yelling at me from the far end. And I was running off the field, something else was said. And after that it was over."
But not before a red-faced Showalter bolted from the first-base dugout, gesturing angrily and shouting at Girardi before being held at bay by Hickox. Girardi followed from the third-base dugout in calmer fashion as players from both teams spilled onto the field.
"It strikes a chord in me and I stand accused," Showalter said.
Once order was restored -- and both benches were issued a warning about any retaliatory measures -- television cameras showed Showalter shaking his head and glaring at Girardi from the Orioles dugout.
"Two competitive good teams and we're fighting for the same thing, so there's a small margin for error. ... But Bobby's not giving pitches," Showalter said.
Alex Rodriguez and Lyle Overbay hit home runs for the Yankees. Rodriguez's first-inning blast to right-center was the 652nd of his career, leaving him eight short of tying Willie Mays for fourth place all-time.
CC Sabathia (13-12), who came into the game with an 18-5 career record against the Orioles, yielded four runs -- three earned -- and seven hits over 7 1/3 innings. He walked two and struck out six.
The Orioles were 2 for 29 with runners in scoring position in their last two games, and their percentage improved in the opener of the critical series, as they went 2 for 8 in such situations.
Still, Baltimore had to manufacture two runs, which scored on sacrifice flies.
"I mean, it"s that time of the year, you know, and that's what those situations call for," Sabathia said. "You're trying to get the runner in from third and get runners over and just get runs however you can. So they did a good job of that."
Baltimore went ahead in the fifth when J.J. Hardy doubled into the left-field corner and advanced to third by beating the relay from first base on Michael Morse's third-to-first groundout. Wieters' sacrifice fly scored Hardy.
Alexi Casilla followed with a single past Rodriguez at third, stole second and came home on Markakis' single.
In the seventh, the Orioles added an insurance run when Machado's 49th double, a two-out poke off the scoreboard in right, scored Wieters from third.
Overbay's homer leading off the eighth chased Tillman.
Yankees SS Derek Jeter, sidelined with a sore left ankle, took Monday off from baseball activities and will be re-evaluated Tuesday, said Girardi. ... Rodriguez batted second, his first time in that position in the batting order since Aug. 26, 2006. ... The Yankees reinstated OF Zoilo Almonte (sprained left ankle) from the 15-day DL. He missed 45 games. ... The Orioles sent IF Alex Liddi outright to Triple-A Norfolk after he cleared waivers. Liddi was designated for assignment Sept. 6.