MILWAUKEE -- Addison Russell took a quick step to his left and snared the sharp one-hopper off the bat of Tyler Austin before the ball could skip into left field. The Cubs' shortstop shifted out of a slide to his feet, gathered himself and fired the baseball across the diamond.

That was the beginning of the end for the Cubs on Saturday night.

"I just sailed it," Russell said in the wake of a 3-2, walk-off loss to the Brewers at Miller Park. "I just sailed it. In that situation, you have to be on point, especially where we're at during the season, coming down to the wire."

• Box score

The situation was this: Ninth inning with the Cubs and Brewers in a 2-2 deadlock. The bigger-picture situation carries more weight: Russell is starting at shortstop in place of the injured Javier Báez, who is likely out the rest of the season after an MRI exam on his ailing left thumb revealed a hairline fracture.

Layered on top of all of that is the fact that the Cubs -- a club that lost the division to Milwaukee in Game 163 last year, only to then exit the October stage with a loss to the Rockies in the National League Wild Card Game -- are clinging to postseason hopes right now. St. Louis has a 3 1/2-game lead atop the NL Central, and the D-backs are only 1 1/2 back of Chicago for the second NL Wild Card.

"It's a huge blow, what happened to Javy," said Russell, who hit a solo home run in the fifth inning. "I'm happy to step up and take on that role. I have a lot of confidence in myself and in my abilities. So, I believe if I just get to work and fully commit to that, I think I can go back to being the type of ballplayer that I know how to be."

Naturally, Russell's errant throw in the ninth made it possible for Christian Yelich -- the reigning NL MVP and a front-runner to take home the trophy again this fall -- to find his way to the batter's box in the final frame.

"Yelich, it's like a Bonds moment, for me," said Cubs manager Joe Maddon, referring to how Barry Bonds impacted games in his prime.

Austin led off the ninth as a pinch-hitter for the Brewers and sent a pitch from Cubs reliever Brandon Kintzler rocketing to Russell's left at 107 mph, per Statcast. Russell's throw pulled first baseman Anthony Rizzo off the bag, allowing Austin to reach easily. It was a tough defensive play, but it also resulted in Russell's third throwing error in as many games.

That is a concern for the Cubs, who are counting on Russell as the main replacement for Baez down the stretch. Russell has plenty of experience at shortstop -- that was his spot on the diamond during Chicago's 2016 World Series run -- but he has spent most of this season playing second base due to Baez's presence.

Lately, Russell has been working on the throwing issue in pregame infield sessions with Brian Butterfield, the Cubs' third-base coach and infield instructor.

"He's spent so much time at second base working on a different [arm] stroke," Maddon said. "Now, he has to go on the other side and get the other one back. I actually think that his arm strength looks better and Butter concurs. So I just think it's a matter of angles."

Kintzler set down the next two batters he faced, retiring Trent Grisham with a flyout to left field before striking out Yasmani Grandal. That prompted a mound visit from pitching coach Tommy Hottovy to talk things over with Kintzler with Yelich looming. Walking him was one way to go, but that would have put the potential go-ahead run in scoring position.

"That's why you don't bunt -- so they do pitch to him," Brewers manager Craig Counsell said.

Kintzler entered the night with a .139/.225/.250 opponents' slash line in 80 plate appearances against left-handed batters this season. In his career against Yelich, the righty had held the slugger to a 1-for-9 showing with no extra-base hits. Kintzler's first two pitches were sinkers -- one at the bottom of the zone and another on the outside edge -- and he got a pair of strikes.

"I felt actually pretty good about it right there," Maddon said. "I know he's a good hitter and everything, but Kintzler was throwing the ball really well."

Yelich spit on a couple pitches in the dirt, fouled off one more and then Kintzler fired an outside sinker. The Brewers outfielder flicked the 2-2 pitch deep into the left-field corner, well out of the reach of Cubs outfielder Kyle Schwarber. The ball dropped in, kicked off the wall and bounced away enough to allow Austin to complete the sprint home.

Yelich raised his arms in the air in celebration as his teammates poured onto the field. Kintzler made the slow walk back to the visitors' clubhouse.

Russell knew that the inning's unraveling could be traced back to him.

"Nobody feels worse than he does right now," Maddon said. "The play he made, first of all, to catch the ball was outstanding. It's just the ball's running on him. There's things you can do to correct that to straighten that out, and that's what he's going to have to do."