In his fourth Arizona Fall League game, Kelly smacked a triple, a double, plated four runs and scored another in the Mesa Solar Sox's 12-5 win Wednesday over the Scottsdale Scorpions.
"I wanted to be aggressive," he said. "I got some pitches to hit. The first one I hit the other way and then, in my third at-bat, I got a changeup that I was able to hit for a double.
"I didn't have many at-bats to end the year. The big thing is to try and get in the at-bats."
The Red Sox decided to have their prized prospect pitch 100 innings during the regular season and then shifted the right-hander to shortstop. He went 7-5 with a 2.08 ERA in 17 starts between Class A Advanced Salem and Class A Greenville. He hit .222 with 22 runs and 16 RBIs in 40 games between Greenville and the Rookie-level Gulf Coast League affiliate.
Kelly might not think he has an "edge" on the pitchers he's facing when he digs in at the plate, but there are moments when it might lean his way.
"I try not to overthink anything too much," he said. "But sometimes if a pitcher's struggling, I kind of understand what's going through his mind."
He's played a ton of ball, but Kelly was still excited about coming to the AFL on the heels of instructional league so he could watch how other marquee players handle themselves. He's already learned one trick of the trade in his brief stint.
"You have to pace yourself," Kelly said. "It's been a long season already. You don't want to get too tired. So you're not taking 10,000 ground balls, but you're taking them at game speed."
Does he miss pitching? "Not right now," Kelly deadpanned.
Kelly, who played third Wednesday, got a closeup look at a superb start by Mesa's Andrew Cashner (1-2). The Cubs' right-handed prospect didn't allow a hit and struck out four over four scoreless innings. He walked two.
Bryan Petersen (Marlins), who is hitting at a .409 clip with Mesa (5-9), collected two hits (including a solo homer), two RBIs and two runs. All eight position players drove in at least a run for the Solar Sox.
Steve Susdorf (Phillies) lofted a two-run homer and Brandon Crawford (Giants) added a solo shot for Scottsdale (6-8).
Rockies righty Chaz Roe (0-1) didn't get out of the first inning and suffered the loss. He was tagged for five runs -- one earned -- on three hits and two walks. He struck out two.
Paige Schector is an editor for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.