ATLANTA -- Cubs rookie Daniel Palencia waited while Braves star Ronald Acuña Jr. pulled second base out of the dirt and hoisted it skyward in the 10th inning on Wednesday night. The reliever stood by as a video montage played and the Truist Park crowd roared in celebration.

The moment was well-deserved -- Acuña became the first player in MLB history to have 40 homers and 70 steals in one season -- but it was another stressor for a member of the Cubs’ taxed and tattered relief corps. One pitch later, Palencia gave up a walk-off single to Ozzie Albies, sending the Cubs to a 6-5 loss and dropping Chicago out of the current postseason field.

“We believe in the group,” Cubs outfielder Ian Happ said. “We've got four games left to get this thing done.”

• Games remaining (4): at ATL (1), at MIL (3)
• Standings update: The Cubs (82-76) sit just outside the third and final National League Wild Card spot. The Marlins (82-76) are tied with Chicago, but own the tiebreaker between the two clubs. Both teams are two games behind Arizona (84-74). Arizona also owns the tiebreaker over the Cubs.

Following a stellar six-plus-inning showing by starter Jameson Taillon, the Braves chipped away and ultimately prevailed against the Cubs’ bullpen. Manager David Ross has been pulling all the levers he has available, but injuries and other issues have piled up and rendered his former late-inning recipe moot.

The Cubs have been operating without closer Adbert Alzolay and veteran Michael Fulmer -- two key arms currently on the injured list. Mark Leiter Jr., who had not pitched in a week, entered for a save and then allowed a game-tying homer to Marcell Ozuna in the ninth inning.

“We're not at full strength, for sure,” Ross said.

In the hours before Wednesday’s loss -- the second heartbreaker in a row for the North Siders -- Cubs president of baseball operations Jed Hoyer took a seat in the visitors’ dugout and discussed the bullpen situation. It was an aspect of the roster that could have been addressed more last offseason and at the Trade Deadline.

“At the Deadline, we had a lot of factors,” Hoyer said, “and there weren't really arms that we felt like we could access at that time. And you look around, a lot of teams had the same challenge. I think it comes down to just building up that depth, and I think you're ultimately going to have to rely on player development.

“For a huge chunk of the season, I think that was effective. It hasn't been effective late, so yeah, I have to look at myself and say, ‘What are we going to do differently for next year?’”

The fact that the Cubs are even in this position -- attempting to punch their ticket to the October stage with four games to go -- is a credit to the bullpen’s mid-season production. After a rough May (5.19 ERA) for the ‘pen, Ross had Alzolay emerge as a closer, with Leiter, Fulmer and Julian Merryweather stepping up as the main setup arms.

The Cubs slipped to 10 games under .500 (26-36) on June 8, but then rattled off a 50-28 record through Sept. 6. From June 9 through the end of July, Chicago’s 3.03 bullpen ERA ranked first in the Majors.

“We got to a place of real stability for a long time and had a really good bullpen,” Hoyer said. “Obviously, the guys that we're relying on six, seven, eight, nine right now are often not the guys that we were for a long time. And at this point we just have to figure it out.

“Other teams are in that position. We have to piece it together in a different way. We had a pretty good formula going for a long time. That formula is not there anymore. So you've got to find a new one.”

Lefty Drew Smyly moved out of the rotation and into the bullpen and has played an important role, including escaping a jam in the seventh on Wednesday to hold the Cubs’ lead to 3-2. Jose Cuas -- acquired at the Deadline -- also navigated through a dicey situation in the ninth, keeping the game deadlocked and forcing extras.

“There are so many dudes that have come through for us all year,” said Happ, who homered in the loss. “That stretch that we had mid-May all the way through August, mid-September, just unbelievable stuff. Those guys take the ball every single day. They’re working hard.”

Prior to Wednesday’s game, Alzolay threw 20 pitches in a live batting practice workout at Truist Park. After that session, the closer said he hoped to come off the injured list on Friday, and admitted that it has been hard to be on the sidelines over the past two weeks.

“You just see the guys out there competing every single day,” Alzolay said, “and just giving everything they have. It’s something that really drives me to keep pushing.”

If the Cubs do get into the playoffs, the bullpen will remain a key factor in how long the team’s October run lasts.

First, the North Siders have to get there.

“I thought we brought it today,” Cubs second baseman Nico Hoerner said. “Just like we’re going to bring it tomorrow and the next day, and trust that in the next four games, that plays out as best it can. That’s what we can control.”