The 6-foot-3, 195-pounder gave up three hits and an unearned run while fanning two and walking one Monday night.
"I felt good out there," Kelly said. "My fastball was in the zone and I was throwing it for strikes. It was good to get the first start out of the way."
Kelly, a 2008 first-rounder, started before 3,964 at New Britain Stadium. The right-hander came in on a strict 50-pitch count and finished with 45 en route to the Sea Dogs' 8-2 victory over the Rock Cats.
Kelly entered the first inning with a comfortable lead after Portland put four runs on the board.
"The start was made a lot easier going in with a lead like that, so it made me calm down," Kelly said. "The first inning challenged me when a couple of runners got on base, but it was good to feel that pressure and work with it."
There was a brief scare when 2009 Futures All-Star Game MVP Rene Tosoni hit a line drive up the middle that caught a piece of Kelly's glove before it could hit him in the chest. After a brief mound visit by the team trainer, Kelly smirked and resumed the inning.
"Thank God I got my glove on it," Kelly laughed. "It was past me before I knew what was happening. I hit the ground and asked myself "Am I all right? Is anything hurt right now?'"
Joe Benson scored on a wild pitch by Kelly for the unearned run.
The 20-year-old threw mostly fastballs around the low-90s, but it was his changeup that batterymate Luis Exposito said worked best.
"His changeup was effective and he executed," Exposito said. "He looked good, confident and had good control. I've always been impressed with him since catching him in Salem. For a young guy, he's always had a veteran look out there and that's most important."
Kelly said his next four to five starts probably will continue to be around 50 pitches in length so he won't have to be shut down later on in the season.
Matthew Stucko is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.