"I knew I had hit it good. I was just hoping it would get a couple runs in," Monroe said. "I knew it didn't have to be a grand slam."
Oh, but it was. The ball soared through the rain and the wind over the center-field wall, and the Tigers held on to beat the Baltimore Orioles 4-1 Wednesday night.
Monroe's first homer of the season was his third hit of the game and third career grand slam.
"He wants to be up there in those situations," Detroit manager Jim Leyland said. "He got the big one."
Ivan Rodriguez opened the 12th with a single off Birkins (0-1), the eighth Baltimore pitcher. With two outs, Magglio Ordonez reached on an infield hit and Carlos Guillen walked before Monroe recorded his clutch hit on a 1-1 pitch.
"We just kept grinding it out, trying to get the big blow," Leyland said. "Sooner or later it was going to come from one of the teams. Fortunately, it came for us."
It was Birkins' first appearance of the season, but he refused to blame his inactivity for the loss.
"I've been throwing in the bullpen to keep fresh so I wouldn't consider myself rusty," the left-hander said. "It was just one of those things. I just left one pitch up and got punished for it."
Wilfredo Ledezma (1-0) allowed one hit in two innings for the win.
Bobby Seay balked in a run the bottom of the 12th. After Melvin Mora hit a two-out double, Todd Jones recorded the final out for his fifth save. He has closed each of the Tigers' five wins.
The Orioles managed only one run in the final two games of the series after beating Detroit in their home opener.
"They're better hitters than that. We know that," Baltimore manager Sam Perlozzo said of his offense. "We've just got to have a little patience with them. They're going to come around and score some runs when we don't pitch so well. Hopefully that happens quickly."
A crowd of 13,288 -- the second-smallest in the 16-year history of Camden Yards -- showed up on a night when the temperature dipped into the 40s. Many of the fans left after the ninth inning, when it started to rain.
Detroit starter Justin Verlander gave up three hits in seven scoreless innings. He walked three, hit a batter and struck out five.
"I did all I could to keep us in the game, and the relievers did all they could," Verlander said. "That was a big part of the win."
Verlander, who won 17 games last year to earn AL Rookie of the Year honors, has not given up an earned run in 13 innings this season but is 0-0 after two starts.
Orioles starter Adam Loewen left after throwing 95 pitches over five innings. He allowed five hits and four walks, hit a batter and struck out four.
John Parrish came in and struck out the side in the sixth. He was followed by Chad Bradford, who worked a perfect seventh.
Danys Baez entered in the eighth and gave up a one-out double to Guillen before striking out Monroe. After Sean Casey received an intentional walk, Brandon Inge grounded out to third.
Before Birkins came in, the Baltimore bullpen allowed two hits over six innings.
"I thought they did a great job. We went all the way to the 12th inning without giving up a run," Perlozzo said.
Kevin Millar and Corey Patterson hit two-out singles in the second inning before Verlander walked No. 9 hitter Paul Bako to load the bases. Brian Roberts followed with a routine fly ball to center.
In the third inning, Verlander hit Miguel Tejada in the back with a fastball. In the fifth, Loewen plunked Gary Sheffield with a two-out pitch, prompting home plate umpire Bruce Dreckman to warn both teams. Ordonez then singled and Guillen walked to load the bases before Loewen concluded his night by striking out Monroe.
- Inge singled in the fourth inning, his first hit of the season after an 0-for-20 start.
- Roberts went 0-for-6 and is batting .139.
- Detroit's Placido Polanco went 0-for-6, the first time in eight games this year he was held hitless.
- Sheffield went hitless in four official at-bats. He's in an 0-for-15 skid that's dropped his average to .103.