PHOENIX -- Madison Bumgarner is looking for every angle to stick with his strong stuff at home.

The D-backs lefty switched his setup on the pitching rubber in Wednesday night’s start against the Pirates. It worked through a few innings, but Pittsburgh broke through late to hand Arizona a 6-4 loss at Chase Field.

Bumgarner had won four of his past five home starts, and the D-backs were vying for a fourth straight win. And on a night when he piled up eight strikeouts through six innings, Bumgarner’s adjustments saw him deliver from the third-base side of the rubber. It was the opposite strategy from his previous outing, when he worked from the first-base side and allowed five runs in a no-decision against the Rockies on Aug. 5.

“I’m just trying to do what I can,” the 2014 World Series MVP with the Giants said. “I moved to the first-base side thinking that the angle would help give me a little more of an advantage. I’ve been over there before, and gone back and forth most of my career. But after the last game, I didn’t feel like I was getting the advantage I was looking for, so then I just went back to where I’ve been.”

Bumgarner successfully grinded it out for much of his outing. Until the sixth inning.

Pittsburgh’s Rodolfo Castro tripled on a deep drive that was a tough play for Arizona’s Daulton Varsho in right field. The very next batter, Greg Allen, also twisted up Varsho with a liner that went for a double. Tucupita Marcano followed with a run-scoring base hit, which widened the Pirates’ lead to 5-2.

That got the D-backs’ bullpen stirring. Bumgarner did not come out for the seventh inning, and he dropped to 6-11 on the season.

“There were a number of strikeouts, he kept making pitches, and it was turning out to be a typical Bum outing,” skipper Torey Lovullo said. “But it unwound on him two outs in the sixth. That was really the difference in the game.”

The D-backs had one more rally in them by the bottom of the ninth. Only a wild sequence that Lovullo admitted he’s never seen before would end the threat.

Varsho led off with a single to right off Pirates reliever Wil Crowe, followed by a first-pitch swing from Emmanuel Rivera for a single to left that moved Varsho to second base. That brought up designated hitter Seth Beer as the potential tying run and a Chase Field crowd got pumped up late.

Beer walked on four pitches to load the bases for eight-hole batter Carson Kelly, who now represented the potential winning run. A ground ball to third base scored Varsho, but that’s when things got weird.

After a rundown, Rivera and pinch-runner Sergio Alcántara both ended up at second base. Alcántara was forced out on the play and Rivera, who was caught between second and third, retreated to second but was tagged out when he stopped short of stepping on the bag because he thought Alcántara was still in play. They were both out.

A replay review ensued and confirmed a rare 5-4-6 double play.

It was a sequence that Lovullo had never seen before, and he said it did lead to a refresher course for the players about which unoccupied bases are safe to return to, or not.

“It’s easy to sit back when there’s zero stimulus in your living room and you’re watching, and you’re unfolding it slowly piece by piece. It’s easy to figure out what’s happening,” Lovullo smiled. “But when you’re in it, right in the middle of it, it’s just a reaction play.”

With two outs and Kelly still at first, pinch-hitter Jordan Luplow flied out to right to end it and halt the D-backs’ three-game winning streak.

Arizona will look to bounce back in Thursday’s series finale after taking the first two in this four-game set before heading out on a seven-game road swing through Colorado and San Francisco. Starting on Friday, the D-backs will play 12 of their next 15 on the road.

“It’s huge, but I think it’s more about winning the series,” Varsho said of Thursday’s last home game before the trek. “Just taking care of business here and then moving onto the next one.”