Wolf and Kelly will face off again on Friday as the Brewers and Cardinals start a three-game series at Busch Stadium.
It's been a rocky season for Wolf. His ERA sits at 5.45, and he's allowed four or more earned runs in 10 of his 20 starts.
"I've had my own personal demons to deal with, my own frustrations," Wolf said. "It's been tough emotionally, more than anything."
He's been better since the All-Star break, posting a 3.66 ERA in 19 2/3 innings. Over that span, he has struck out 17 batters and walked five.
Against the Nationals in his last start, Wolf started his outing with three hitless innings before Washington scored three runs in the fourth and one in the fifth.
"I had that rough fourth inning and made a couple mistakes," Wolf said. "Other than that, I felt I threw the ball a lot better. You still give up four runs, it's not a great outing. But I thought for the most part I threw strikes, and I was aggressive and made some pitches when I needed to and got out of some jams."
Kelly, a rookie, has been very consistent in his nine starts so far this season. He's pitched exactly six innings on six different occasions. He hasn't thrown more than 100 pitches or allowed more than three earned runs.
The right-hander pitched into the seventh inning for the first time in his career on Saturday, retiring one batter in the seventh before making way for the bullpen.
"Now it's under my belt that I can get past it," Kelly said. "I was just a few pitches away from going even farther."
Brewers: Gomez's change in approach working
Over the last few weeks, outfielder Carlos Gomez has tweaked his approach at the plate, adding a leg kick that helps him "drive balls more easily out of the ballpark."
The changes seem to be working -- Gomez is batting .351 (13-for-37) with four homers and 10 RBIs in his last 10 games, and was named the National League Co-Player of the Week last week.
Cardinals: 1982 World Series championship team to be honored
The Cardinals and their fans will spend this weekend's series celebrating the 1982 World Series champions, as more than 20 members of the team will reunite at Busch Stadium.
Yadier Molina, who sprained his right thumb in Wednesday's game, and Lance Berkman, who re-injured his surgically repaired right knee in the ninth inning of Thursday's game, will also be evaluated by team medical staff Friday.
Cardinals third baseman David Freese is batting .385 against Wolf in 26 career at-bats.
The Brewers are just 6-15 when Wolf takes the mound this season.