The Braves' No. 6 prospect teamed with No. 5 prospect Christian Bethancourt to dominate on the mound, but Mississippi lost to the Mobile BayBears, 1-0.
Gilmartin allowed leadoff singles to Marc Krauss and Archie Gilbert in the second and sixth innings, respectively. The left-hander, who said he was troubled at times by his fastball command, retired 11 straight in between the base knocks. He did not strike out or walk a batter.
"I'm always going to be around the zone," Gilmartin said. "That's just me making my pitches."
Gilmartin threw 43 of 71 pitches in the strike zone. He said he would like to throw 80-90 pitches in his next outing.
Atlanta selected Gilmartin with the 28th overall pick in the 2011 Draft. The Florida State product made his first six pro appearances between the Gulf Coast and South Atlantic leagues last year. He also pitched in eight Arizona Fall League games, going 2-1 with a 4.34 ERA and a 26-to-8 strikeout-to-walk ratio.
Gilmartin spent much of his time in the greater Phoenix area alongside Bethancourt, who also was a member of the Surprise Saguaros.
"We worked together a lot in Arizona," Gilmartin said of Bethancourt, who batted .306 with five homers in 19 AFL games. "He knows me pretty well and I know him pretty well. We had good chemistry tonight."
Bethancourt also contributed at the plate, not simply behind it. The 20-year-old Panamanian singled twice in four at-bats but was left stranded each time.
"The guy can flat-out hit," Gilmartin said. "I wouldn't be surprised if he hits double-digit homers in this league."
Oh, and one other thing.
"He has one of the best throwing arms I have ever seen," Gilmartin added.
BayBears starter Derek Eitel allowed four hits and issued two walks but left after four shutout innings. Bryan Henry and Kevin Munson (1-0) each worked two scoreless frames before Matt Gorgen earned the save in the ninth.
The defending Southern League champions scored the game's lone run in the top of the ninth, when Krauss' two-out single off reliever Mark Lamm brought Adam Eaton home from third. Like Bethancourt, Krauss went 2-for-4.