Duffy is scheduled to play in Port Charlotte on Thursday night.
"I feel good," said Duffy, who was at Tropicana Field prior to Wednesday night's contest between the Rays and Royals. "Played four innings. It was a pretty long four innings.
"We batted around in the first, so there was a little bit of sitting around on my part there. And there was a pitching change in the third. Our pitcher had a little issue with his forearm, but I heard he was doing good. It was a good test of keeping it warm. Sitting down and getting back up again. Feel good, feel good today. No soreness. All positives."
The Rays acquired Duffy in the four-player trade that sent Matt Moore to the Giants on Aug. 1, 2016. Duffy took over as the starting shortstop after the deal and did not make an error in 18 games (55 chances and 153 innings) at the position. He hit .276 with a home run and seven RBIs before having season-ending surgery in Charlotte, N.C., to remove the bursa from the heel and debride the bone abnormality.
At the outset of Spring Training, Duffy felt like he would be ready to go by the middle of March. That projection, obviously, has dragged on.
Duffy believes he can be ready for Major League action in two weeks. He was asked about strides he made on Tuesday while going 1-for-3 in his first game since Sept. 5, 2016, against the Orioles.
"The biggest thing for me is taking batting practice, sitting back down for an hour, hour and a half, then getting back up again," Duffy said. "That was good, because I haven't had to really do that yet.
"Second at-bat I moved a guy over, and I was able to execute it, so that was cool. I wasn't going to be too hard on myself at first, but it was nice to see those results right away."
Duffy said he hit a line drive in his third at-bat.
"I didn't crush it by any means, but the trajectory was good off the bat, so I was happy with that as well," Duffy said. "Really, my goal yesterday was just to see some pitches and see it deep, and try and trust my hands. Seeing it deep was pretty easy since the first guy throwing was mid 90s, of course."
Duffy said he "felt good overall."
"Even tried to steal a base, but it was a foul ball," he said. "So I wouldn't have done that if I didn't feel good either. All positives. I think as I go forward, the biggest thing for me is staying on my feet for a long period of time, and trying to get my timing back. And eventually, in a week or so, try and catch some balls out front and be a little more aggressive in terms of contact point. And getting close to being full-game ready up here."