ST. LOUIS -- It had been 47 days since the Cardinals last lost with Joe Kelly on the mound. During that near seven-week stretch, he had been the rotation's best, pitching the team out of its three longest losing streaks of the second half and stabilizing a staff that, at times, looked to be coming unglued.
On Thursday, however, a sloppy start in front of 43,866 at Busch Stadium did Kelly in.
A wild pitch and Kelly's own pair of throwing errors aided the Brewers early in what would settle as a 5-3 win over the Cardinals. There would be no series sweep for St. Louis, but rather an end to the team's five-game winning streak and to Kelly's league-best active winning streak of eight.
The division also got a bit more crowded by night's end, as the loss opened the door for Pittsburgh to slide back into a first-place tie. The Reds, idle on Thursday, loom 2 1/2 games back in the National League Central.
"This game just came down to we made too many mistakes," manager Mike Matheny said. "You make too many mistakes and can't get your offense going, it doesn't always turn out well."
The mistakes weren't solely on Kelly, though that's where they started. The right-hander had all sorts of issues in the first two innings, though few of them had to do with anything the Brewers initiated. A wild pitch in the first advanced a pair of runners, one of whom then scored on a one-out groundout.
A pair of errant throws in the field cost Kelly another run in the second. There was a muffed pickoff attempt first, allowing Logan Schafer to move from first to third. Schafer scored on a grounder that shortstop Pete Kozma couldn't stop, and two batters later, Kelly cost himself an out when Milwaukee tried to hand him one with a sacrifice bunt.
A double play helped Kelly escape the inning without further damage, but his pitch count (then at 40) had already suffered. The Cardinals would never climb out of the hole, either, as they lost to the Brewers for just the fourth time in 16 games.
"It wasn't too good all around," Kelly said. "Early in the game, they were swinging early at the fastball and getting some hits. I could have made some better pitches. … Throwing away a couple balls was a deciding factor. Take away those two runs and it's tied."
Brewers first baseman Sean Halton further cut into the Cardinals' hopes of another comeback win when he drilled the fourth pitch of his fourth-inning at-bat over for a two-run homer. Halton, who finished with three RBIs, has driven in nine runs this season; seven have come against the Cardinals.
"It was nice to be a factor tonight," Halton said. "A guy like me, being called up for September, that's all you can really ask for is to be a factor."
For Kelly, the four runs (three earned) allowed tied his season high. He had given up just five in his previous five starts (30 innings) combined. The five-inning start was also his shortest since permanently moving into the rotation in early July.
"Joe has been so good for us and really battled to stay in there," Matheny said. "You look at how he did limit the damage, kept us in that game. I think it really could have gotten out of control. [He] looked pretty close to what we've seen, but once again the mistakes got him."
Outdueling Kelly was Tyler Thornburg, who was rewarded with his first career win as a starter. Jon Jay and Matt Holliday gave him trouble throughout the night, but Thornburg was able to silence the rest of a Cardinals starting lineup sans Yadier Molina for a second straight night.
The Cardinals provided some undesired assistance, too.
There was an unsuccessful sacrifice attempt by Kelly in the third -- he struck out with one out and one on -- and twice runners were erased on the bases. Jay was caught stealing in the opening frame; Matt Carpenter was caught straying too far from first on a line drive-turned-double play in the eighth.
"We just couldn't do anything against him," Beltran said. "Right now, we're not finding a way to score early. We need to change that."
The Cardinals cracked Thornburg in the fourth to halve the four-run deficit. Jay singled and scored on a double by Holliday. A pair of deep flyball outs brought Holliday home, too. Jay and Holliday both reached again in the sixth, but Thornburg stranded the potential tying runs by retiring Beltran and David Freese.
The Cardinals wouldn't score again until the ninth, when Matt Adams connected for his 13th home run.
Thornburg, now 1-0 with a 1.50 ERA in his five Major League starts, has found success at this level after starting his season 0-9 with a 5.79 ERA in 15 Triple-A starts. He smiled afterward when asked about playing the role of spoiler.
"I know [former Cardinal] Kyle Lohse wanted to throw so he could do that," Thornburg added. "He wanted to be the guy that makes [the Cardinals] go to that Wild Card game or whatever. I know he wanted that, so I was trying to do the best I could to help him out there."
Lohse would have pitched on Thursday had the Brewers not shifted to a six-man rotation beginning this week. As it is, he'll miss them again, too, when the Cardinals make their final visit to Miller Park later this month.
Those will be three of the 16 games the Cardinals have left as they try to create some division separation. For the last 27 days, the Cardinals and Pirates have been no further than two games apart in the division standings.
"Those guys are playing good baseball. We're playing good baseball," Kelly said. It's going to be a fun run toward the end."
Jenifer Langosch is a reporter for MLB.com. Read her blog, By Gosh, It's Langosch, and follow her on Twitter @LangoschMLB. This story was not subject to the approval of Major League Baseball or its clubs.