CINCINNATI -- What started as a mutual slugfest on Sunday afternoon at Great American Ball Park turned into a Cubs rout in the late innings.

All-Star closer Alexis Díaz jogged to the mound in the eighth for a rare appearance outside of the ninth inning. But it still fit the bill for a high-leverage situation in which you’d want your best pitcher: Tie game, bases loaded, no outs.

Instead of escaping the tough jam, like he’s done so many times this season, Díaz gave up a two-run single. He let two more runners reach (one on an error) before he was pulled, as the Reds’ bullpen allowed a season-high seven runs in one inning, all but assuring an eventual 15-7 loss to the Cubs.

• Games remaining: vs. SEA (3), vs. STL (3), at DET (3), at NYM (3), vs. MIN (3), vs. PIT (3), at CLE (2), at STL (3)

• Standings update: The Reds (71-68) are in a virtual tie with the Giants (70-67), D-backs (70-67) and Marlins (70-67) for the third National League Wild Card spot. The Reds have the tiebreaker over the D-backs, while they’ve lost the tiebreaker to the Giants. They also have the tiebreaker over the Cubs (73-64), who hold the second Wild Card. The Reds have tied the season series with Miami. In that case, the tiebreak will come down to intradivision record, which has not yet been determined, although the Marlins have the edge.

“It's a tough spot for [Díaz] to come into and to be asked to get out of that,” manager David Bell said. “So I wouldn't let today really be an evaluation point on how Alexis is doing. He's having a fantastic year for us, he's doing a great job.”

The Reds’ bullpen has been one of the best in the league for much of the season, but the rare meltdown ended the duel that had been brewing for the first seven innings. Including the seven-run eighth inning, 12 runs marked the most allowed by Cincinnati’s relief corps since June 1, 2021, against the Phillies. Of the four times the bullpen has allowed at least 10 runs this season, three have come against the Cubs.

After Díaz allowed three runs (one earned) without recording an out for the first time in his career, Bell was forced to make a pitching change. He brought in Brett Kennedy, who he had originally hoped would start on Monday as the Reds build a rotation from scratch following a COVID outbreak. Kennedy, the seventh pitcher of the game for Cincinnati, covered the final two innings while allowing four runs to save more relievers for what will likely be a tough series against Seattle.

“That was kind of the end of the line for where we were with available innings,” Bell said. “We needed to save guys that were available to pitch tomorrow, but that was pretty much it as far as who we had available. ... Not ideal, but Brett being able to go the last two innings puts us in a better situation for tomorrow.”

While the Reds’ bullpen couldn’t take care of the Cubs, Carson Spiers certainly did in his MLB debut on Sunday. The 25-year-old was added as a substitute player from Double-A Chattanooga, as Cincinnati has four players on the COVID-19-related IL.

Spiers started off shaky, allowing a hit to his first batter and a run in each of his first two innings. But he settled in as he recorded a perfect third and fourth inning. Spiers struck out two batters each in the third and fourth, and he recorded seven strikeouts over his start, becoming the first Reds pitcher since Hunter Greene to strike out seven batters in his debut.

“The adrenaline wore off in the third, and it was more of just go time,” Spiers said. “I felt like my pitches were kind of more sharp, whether that was being out in front of them or just being more relaxed on the mound. That third inning is definitely where I need to be.”

It hasn’t been an easy journey to the Majors for Spiers, who signed with the Reds in June 2020 as an undrafted free agent out of Clemson. He bounced between starting and relieving in his first two seasons in the Minors, then he was firmly ensconced in Chattanooga’s bullpen at the beginning of the season. But as other Cincinnati prospects got the call to Triple-A Louisville, Spiers once again found himself in the rotation.

The Greenville, S.C., native had around 15 friends and family on hand to witness his debut, some making the six-hour drive from his hometown, while others flew in from even farther away.

“He's such a dadgum competitor on the mound,” Spiers’ dad, Michael, said. “His college coach told him he was a bulldog out on the mound, and that's what he's got. That's one of his blessings.”

Spiers, as a substitute player, is not on the 40-man roster and likely won’t stick around once Greene and Ben Lively return next week. But he’s not letting that affect how he works in Cincinnati.

“I'm just going to take it all in, I'm not going to worry about that,” Spiers said. “Whether they keep me here for however long COVID lasts or whatever the decision is, that's out of my control. Can't do anything about it. I'm just going to work my tail off and let everything else happen.”