CHICAGO -- When Tyler O’Neill returned from the 60-day injured list on Thursday, the Cardinals made the bold decision to go away from their usual 13-player, 13-pitcher split and opt for an extra bat during their critical four-game series against the rival Cubs.

That move, of course, further weakened a relief corps that has been the team’s Achilles heel all season. The Cardinals not only entered Saturday’s game with an MLB-high 21 blown saves, but their standing in saves (24, tied for 18th in MLB) was disproportionate to their number of save opportunities (45, tied for ninth).

The Cardinals’ bullpen struggled to provide relief on a soggy Saturday. The club could not hold leads of 1-0, 3-1, 5-3 and 6-5 before losing 8-6 to Chicago at Wrigley Field in backbreaking fashion.

Starter Miles Mikolas was pulled after surrendering a season-high 11 hits and five runs over five innings. His exit meant the shorthanded bullpen had to cover four innings. Zack Thompson, who has jockeyed between starting and relieving all year, allowed two hits and two walks that led to three more earned runs.

“You’re kind of hanging the bullpen out there when you’re asking them to throw four scoreless innings with a one-run lead,” muttered Mikolas, who was a victim of soft contact that repeatedly found holes in the Cardinals’ defense.

By carrying three catchers and a glut of outfielders with Dylan Carlson, Alec Burleson and Dylan Carlson behind starters Lars Nootbaar, Jordan Walker and O’Neill, the Cardinals opted in to carry 14 position players for the first time this season. That will likely change before the Trade Deadline, and there could be roster alterations with big series ahead against the D-backs (three road games) and Cubs (four at home). St. Louis is currently in a stretch of 17 consecutive games without an off-day -- something that undoubtedly puts even more of a strain on the shortened bullpen.

“You know that you are going to be down a man in the ‘pen and you manage accordingly,” said manager Oliver Marmol, who was ejected in the top of the sixth inning after being upset with strike calls to Nolan Gorman and Nolan Arenado.

Last season, the Cardinals rode the All-Star performance of closer Ryan Helsley and some solid bridge work from Giovanny Gallegos and Jordan Hicks and only blew 17 saves en route to 93 victories and a National League Central crown.

This season, St. Louis has 22 blown saves -- often in ways that stagger a squad emotionally. After a recent stretch of improvement that helped the Cardinals string together six straight victories, another lack of relief led to Saturday’s latest crushing loss.

Said Marmol: “We’ve actually done a good job of not [squandering leads] for a while. We’ve used the back end of our ‘pen in [JoJo Romero] and [Chris Stratton] quite a bit over the last seven days, so if you continue to go to those guys, they won’t be available the remainder of the season. We’ve got to be able to go to other guys to bridge to Hicks, and unfortunately, we weren’t able to hold them down.”

Nootbaar hit the first pitch of Saturday’s game for a home run -- the first Cardinals’ player to do that at Wrigley Field since at least 1950 when such statistics started being kept, per Elias Sports. The Cards grabbed other leads when Gorman hit a mammoth 445-foot home run in the fifth inning and when Nootbaar wisely scored on a wild pitch in the sixth.

However, each lead would evaporate. Cardinals' pitchers struggled to get outs consistently against a Cubs lineup that had 15 hits and welcomed the return of shortstop Dansby Swanson, who had a double and an RBI single in the twice-delayed, soggy slog.

“One of the things I want to make sure I do -- if we can scrape together some runs and have a big inning -- is to go out and have a shutdown inning,” Mikolas said. “For those runs to come right after we scored, that’s upsetting.”

Reliever Drew VerHagen, who bounced back from an RBI single by Seiya Suzuki by fanning Christopher Morel and Yan Gomes in the sixth to keep the Cards within striking distance, said he knew all day the bullpens would likely decide Saturday’s game.

“It just felt like that type of game,” said VerHagen, who was activated off the 15-day injured list on Saturday. “We’re not talking about it [in the bullpen], but we’re trying to stay ready because it felt like one of those games where we came in, they would be aggressive. There was a lot of back and forth and unfortunately, we didn’t come out on the right side.”