The rookie right-hander will take the mound for the Padres in Sunday's series finale against Rockies' lefty Jeff Francis, who's coming off a sharp outing of his own.
Kelly gave up only three hits and struck out four in his first big league start against the Braves, allowing only two runners to reach second base on the night -- and none after the second inning.
"It was perfect," Padres catcher Yasmani Grandal said after the game. "He was spotting fastballs, throwing curveballs for strikes, throwing changeups for strikes. He's a three-pitch guy."
Kelly threw a simulated game in Colorado last September, when he and pitchers Joe Wieland and Robbie Erlin joined the club for the final two weeks of the regular season, soaking in everything they could at the Major League level without actually being part of the roster.
Now, he's back in the mile-high atmosphere, looking to put into practice some of what he was introduced to a year ago.
"It was huge. You learn so much by watching," Kelly said. "You get to sit and listen to the veteran guys who have maybe faced a hitter hundreds of times. You watch what the hitters are doing, too. And you start thinking about what you want to do to them."
Kelly will be squaring off against Francis, who displayed excellent command of his fastball last Monday, allowing only three hits and a walk over five scoreless innings against the Dodgers.
Francis needed 91 pitches to get through five innings in that outing, but he has now tossed at least five frames in four straight starts -- no small accomplishment in the Rockies' four-man rotation.
"It's funny, because it's only five innings," Francis said after that outing. "In the world of starting pitchers, it's really nothing to get that excited about. But within our role on this team, it's our job. That's what we go out there to do, so it is very satisfying. But it's weird to stand here and think I did a really good job, because I just threw five innings."
Padres: Cashner, Thatcher return from DL
Pitchers Andrew Cashner and Joe Thatcher returned from the disabled list on Saturday. Cashner hadn't suited up for San Diego since he went on the disabled list on July 4 with a strained right lat muscle, and Thatcher landed on the DL on July 26 with tendinitis in his right knee.
Cashner will work his way back into the rotation at some point next week, likely throwing around 70 pitches after tossing 56 on Friday in a rehab appearance for Triple-A Tucson.
"I'm ready to go," Cashner said. "I got my three rehabilitation outings in and felt good. I worked on some stuff, getting strike one, following it up with strike two, going after hitters early in the count. This month is big for me."
Thatcher, meanwhile, got right back to work, striking out the only batter he faced Saturday. The lefty reliever will still need offseason surgery, and the recovery period is about four months.
"We'll get it fixed," Thatcher said. "They'll go in and remove the damaged tendon and staple the healthy parts together."
Rockies: Tulo may need more rehab
Troy Tulowitzki joined the Rockies on Saturday to be evaluated after playing seven innings Friday with Triple-A Colorado Springs. The shortstop was not activated off the disabled list, however, after playing six rehab games, three at Double-A Tulsa and three more with Colorado Springs.
Tulowitzki had surgery in June to remove scar tissue from his left groin and can be activated at any time if he's deemed ready.
"It's just a matter of picking the right time," Tulowitzki said. "I still haven't been tested on the bases, but I feel good at the plate. I'm getting there."
Colorado only added two players to its roster on Saturday, when clubs were allowed to expand up to the limit of 40: first baseman Jason Giambi and reliever Guillermo Moscoso. Giambi missed 35 games with a viral syndrome, and the 41-year-old came back from his rehab assignment saying he wanted to keep playing in 2013.
Moscoso was in Colorado Springs, where he went 8-6 with a 6.13 ERA in 18 starts. The right-hander was 0-1 with a 7.53 ERA in 13 games, three of them starts, in three prior stints with the Rockies.
The Padres have compiled a 55-55 record since the end of April, including a 42-31 mark since June 12.
Jordan Pacheco extended his hitting streak to 10 games with a one-out double in the fourth inning on Saturday night.