The 19-year-old right-hander yielded just one hit over six scoreless innings, striking out three without walking a batter as the visiting Drive dropped the Rome Braves, 5-1, on Monday afternoon.
A first-round pick of the Boston Red Sox in 2008, Kelly improved to 5-1 while lowering his ERA to a league-leading 1.12.
"I try not to look at the numbers. I just try to go out every outing and compete the best I can," said Kelly, who will convert to shortstop when he reaches 100 innings pitched. He stands at 48 1/3 innings after eight starts.
Bouncing back from his only loss of the year in his previous start, Kelly said he didn't make any specific adjustments heading into Monday's outing but just kept to the formula that has been working so well.
"I pounded the strike zone with the fastball and had the secondary pitches [changeup and curve] both working," he said.
Kelly retired the first 11 batters he faced before yielding a two-out, line-drive single up the middle to Luis Sumoza in the bottom of the fourth.
"It was hit pretty well," he said of the lone blemish in his pitching line. "I tried to get my glove on it, but it was already past me."
Kelly retired the next seven batters in order before being removed after the sixth, matching his longest outing of the season. He also went six scoreless innings against the Augusta GreenJackets on May 14, giving up two hits and three walks for the win.
Kelly played exclusively in the field as a shortstop in 2008 between the Gulf Coast League Red Sox and the short-season Lowell Spinners, but he did work as a pitcher in the instructional league last fall.
Despite enjoying so much success on the mound as a starter this year, Kelly said he is looking forward to the switch back to shortstop.
"I've started out pitching well, and I'll continue to work on that until I reach my innings [limit]," he said. "After I get to my innings, then I'll go back to shortstop. Not a lot of players get to do that, so it's pretty special."
When asked if he's already started working on his swing or his fielding, Kelly laughed. "I started hitting a little, taking some grounders," he admitted, "but I haven't taken full batting practice yet."
Dan Marinis is a contributor to MLB.com This story was not subject to the approval of Major League Baseball or its clubs.