Cobb allowed one run on five hits in four innings, striking out one and walking none. Ronnier Mustelier, the Gwinnett Braves left fielder, homered off Cobb with two outs in the second inning.
"He threw the ball well," said Rays manager Kevin Cash after Saturday's 6-2 loss to the Astros.
Cobb has not pitched in a Major League game since the 2014 season when he went 10-9 with a 2.87 ERA. He had Tommy John surgery early in 2015.
Cobb is 35-23 with a 3.21 ERA in 81 career starts, all with the Rays.
Bill Chastain has covered the Rays for MLB.com since 2005. This story was not subject to the approval of Major League Baseball or its clubs.