PHOENIX — The Arizona Diamondbacks battled the Cincinnati Reds through seven tight innings before letting Sunday’s game slip away, 6-1.

Cincinnati scored five runs in the eighth inning with Spencer Steer hitting the game-opening, three-run home run off Juan Burgos. Two hits for the Diamondbacks set a season low after they scored 10 runs on Saturday.

The D-backs missed out on the chance to sweep the Reds (68-63), a team directly ahead of them in the standings, before embarking a daunting road trip to the Milwaukee Brewers and Los Angeles Dodgers.

Additionally, the Reds captured the season series in this matchup, 4-2.

Arizona (64-67) played well overall during the homestand with series wins over Cincinnati and Cleveland, but that .500 record continues to elude it. The New York Mets remain 5.5 games up on the D-backs for the final Wild Card spot.

Zac Gallen duels Brady Singer

Neither offense found much success against Sunday’s starting pitchers.

Zac Gallen delivered six innings with one earned run and seven strikeouts. The lone run scored during the sixth inning on a little league home run from Noelvi Marte. Marte hit a triple and scored when shortstop Geraldo Perdomo’s throw to third base skipped off Marte’s foot.

Otherwise, Gallen was excellent with a trio of 1-2-3 innings. In five starts during August, since he stayed put at the trade deadline, Gallen has worked a 3.10 ERA.

Reds starter Brady Singer, however, shut down the Diamondbacks after the first inning. Perdomo led off with a triple into right field and scored on a Lourdes Gurriel Jr. sacrifice fly, and from there Singer did not allow another hit through the sixth inning. He struck out eight hitters.

Diamondbacks reliever Kyle Backhus managed to strand the bases loaded in the seventh inning, but the floodgates opened in the eighth, as the Reds sent 10 men to the plate.

In just a few minutes, a competitive game became a blowout. Burgos was tagged with four earned runs, while Backhus was charged with one from an inherited runner.

Arizona had one base runner over the final six innings of the game.

Corbin Carroll reaches 20 steals

Corbin Carroll stole two bases on Sunday to reach 20 for the season. He became the fourth player in franchise history with three seasons of 20-plus stolen bases (Tony Womack, Chris Young and Jake McCarthy).

Carroll has hit 27 home runs and 16 triples with 20 steals this year. The only two players who previously reached those marks in a single season were Willie Mays in 1957 and Jimmy Rollins in 2007.

Diamondbacks begin gauntlet road trip in Milwaukee, Los Angeles

The Diamondbacks face the league’s best team by record in the 81-50 Brewers for four games at American Family Field, starting Monday. Without an off day, the Diamondbacks will travel back west for a three-game set at Dodger Stadium.

By opposing winning percentage, the Diamondbacks face the toughest strength of schedule in Major League Baseball for the rest of the season, and a recent run of improved play will be tested with less room for error.

The Diamondbacks have played both teams tough this season, winning two of three games against Milwaukee back in April. They have a 3-4 record against the Dodgers with three losses by three or fewer runs.

Diamondbacks-Brewers probable pitchers

Monday: Eduardo Rodriguez (5.40) vs. RHP Brandon Woodruff (2.47)

Tuesday: Brandon Pfaadt (4.95) vs. RHP Jacob Misiorowski (4.19)

Wednesday: Ryne Nelson (3.63) vs. RHP Quinn Priester (3.44)

Thursday: Nabil Crismatt (1.00) vs. LHP José Quintana (3.32)

First pitch on Monday is at 4:40 p.m. MST on 98.7 and the Arizona Sports app.