Garcia won his fourth straight start and the Mariners took advantage of two mistakes by Atlanta to beat the Braves 2-1 on Friday night in a matchup between the teams with the two best records in the majors.
"If you have that many wins you must be doing something right," the Mariners' Bret Boone said of the Braves. "I'm sure that was uncharacteristic."
Garcia (7-6), a two-time All-Star and Seattle's ace, lost his bid for a shutout in the eighth on Marcus Giles' RBI double.
Meeting the Braves for the first time in history, the Mariners beat Russ Ortiz (7-4). Seattle matched Atlanta with 44-21 records.
Garcia pitched 7 1/3 innings and allowed one run on seven hits and two walks, with five strikeouts.
"Freddy was unbelievable tonight,'' manager Bob Melvin said. "His confidence is going to keep growing. It looks like he's really turned the corner."
Catcher Ben Davis said Garcia's improvement in his last four starts is more mental than physical.
"I think that's the biggest change we've all seen in Freddy,'' Davis said. "He doesn't let the calls or errors affect him. I think that's all part of growing up."
In 7 2/3 innings, Ortiz gave up both runs -- one earned -- on seven hits, an intentional walk and a hit batter. He struck out one.
"I felt great and we always had a chance," Ortiz said. "We're down 2-to-0 and my job is to keep it right there."
Garcia is 4-0 with a 2.37 ERA in his last four starts after opening the season with a 3-6 record and a 5.90 ERA in his first 10 outings.
The Mariners opened the scoring with two runs in the first, one of them unearned.
Furcal fielded Martinez's grounder and threw to first, but first baseman Robert Fick wasn't covering the bag and Furcal's throw went into the camera well.
Martinez went to second on the throwing error and scored on John Olerud's single.
Fick took the blame for Furcal's error. He thought Martinez's was going to get to the outfield and he positioned himself on the grass halfway to second to take a throw from the outfield. Instead, Furcal managed to stop the ball.
"I saw it get through and the next thing you know he got it," Fick said. "That pretty much lost the game for us."
But Braves manager Bobby Cox was more forgiving about the play.
"He was going to be the cutoff man," Cox said of Fick. "That's what happens sometimes when you have an infielder with that much range. You get fooled every once in awhile."
Andruw Jones made a costly baserunning blunder that turned into a double play in the second. Jones opened the inning with a single before Fick hit a drive to right that Gold Glove outfielder Ichiro Suzuki grabbed with an outstanding over-his-shoulder running catch.
Jones was ruled out for missing second in running back to first after the Mariners appealed the play.
"I don't feel bad about it," Suzuki said through a translator when asked about his catch.
Third baseman Jeff Cirillo was the Mariners' player who noticed that Jones did not touch second going back to first. Jones actually missed second the first time, too.
"He didn't retag on the way back," Melvin said. "Actually, I didn't even see it. Our guys did. Our guys were on top of it out there and that ended up obviously being a big play."
The Braves got their run in the eighth on a single by Vinny Castilla, Furcal's sacrifice and Giles' double to right that Suzuki came close to catching. Shigetoshi Hasegawa replaced Garcia and got Gary Sheffield on an infield popout.
Cirillo went down to the dirt to get the hard-hit grounder. He threw Chipper Jones out at second from his knees.
"I just reacted," Cirillo said. "It felt good to do it.''
The Mariners had their fifth sellout (45,791) of the season at Safeco Field. The Mariners had 36 sellouts last season when they led the majors in attendance for the second straight year with 3.5 million fans. ... The Braves are 5-2 against AL teams this season, while the Mariners are 7-3 against NL teams.