DENVER — Rockies manager Bud Black sank lower and lower from his perch in the dugout as he watched three pitchers walk five to force in two free runs in the top of the sixth Sunday.

The three — Jon Gray, Lucas Gilbreath and Robert Stephenson — combined to throw 45 pitches, only 20 of which were strikes, during the 33-minute half inning. It was the nail in the coffin for the Rockies, who had just five hits in the last game of their homestand. The Diamondbacks won 8-4, ending the Rockies’ bid for a perfect six-game stretch at Coors.

Perhaps they were just getting a jump-start on their road trip, a 10-day, nine-game adventure that includes games against the depleted Cubs, last-place Rangers and the still-alive Dodgers. At this point, the Rockies almost have more walk-off wins (12) than road victories (14).

Starter Gray, who is in the midst of contract extension talks, was off from the beginning. In the second, he allowed a single and a double, then a three-run home run from Daulton Varsho.

He held it together after that, until the killer sixth inning, but the always candid Gray said there was only maybe one good takeaway from his start. That was his curveball, which was effective Sunday. 

“It was just bad all around,” Gray said. “I just didn’t feel good about my rhythm. I didn’t feel good about my grip, I didn’t feel good about my line. There were so many things that just felt off today. I knew today was going to be a battle, but I’m just sick of battling.”

At this point, down just 3-1, the Rockies were very much in the game. But then Gray walked two in a row. He was already at 108 pitches, so Black turned to rookie Lucas Gilbreath, one of two lefties in the bullpen, to face three left-handed batters in a row. Here he was again, a young pitcher the team was trusting in a big situation. He passed his test earlier this week, pitching two scoreless innings. But Sunday was a different story.

Gilbreath inherited the game with two runners on, and walked Varsho, the first batter he faced, to load the bases. He struck out pinch-hitter Carson Kelly on a 79.5 mph slider, but walked Josh Rojas to give the Diamondbacks a run. The lackluster Coors Field crowd announced their displeasure with a round of boos for their hometown reliever. With no lefties left, Gilbreath was replaced by Stephenson, who followed the trend and immediately issued a bases-loaded walk.

“We didn’t shut it down after that,” Black said. “They nicked all of our relievers.”

The Rockies’ offense looked like it was going for a repeat of the performance from Saturday night, when it was absent for eight innings before Garrett Hampson provided some power and Elias Díaz walked it off. But there were no similar heroics Sunday. Ryan McMahon had an RBI double in the first, which drove in Connor Joe, who had been hit by a pitch.

They didn’t get another run until the eighth, when McMahon had an RBI single and CJ Cron had a sacrifice fly. Joe kicked in another run in the ninth off a deep double. 

“We didn’t swing the bats great today,” Black said. “Today was a little bit of a mystery, because their guy was a little wild … we just couldn’t solve him.”