PHOENIX -- Torey Lovullo knows the results haven’t necessarily shown it recently, but the D-backs manager believes that the back end of his bullpen is still a strength of his team.

Friday night it was setup man Yoan Lopez who was touched for a homer by Ronald Acuna Jr. in the eighth inning of what proved to be a 2-1 loss to the Braves at Chase Field.

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Lopez (0-1) had only allowed one earned run this year heading into the game, but his hard-hit percentage was up, as was his line-drive rate.

Acuna’s homer came with two outs after Lopez fell behind 2-0 on Braves’ young superstar.

“You can’t fall behind to a good hitter like Acuna, and he found that fastball down the middle and he didn’t hesitate and he took advantage of it,” Lopez said through interpreter Martin Bater. “I was looking for my best pitch on 2-0, which is my fastball. I was trying to keep it low and outside, and it just stuck in the middle.”

Lopez, 26, made his big league debut against the Braves last year at Chase Field and allowed three runs without retiring a batter. This year, of the only two earned runs he’s allowed, one came against the Braves in Atlanta last month and the other was Friday night.

“The Braves have been the only team that has been able to get me, but it’s all part of the process,” Lopez said. “It’s part of growing, and that’s just how baseball is. Sometimes you just can’t explain it.”

The other parts of the bullpen’s back end have had their struggles recently.

Yoshihisa Hirano has not been as sharp this season; he allowed three runs in two-thirds of an inning Tuesday night in Tampa.

Archie Bradley suffered a meltdown against the Rockies at Coors Field on Sunday, when he allowed five runs (four earned) and did not retire a batter.

Closer Greg Holland, who had been virtually unhittable to open the year, has allowed a run in each of his last three appearances.

“Minimal concern for me right now,” Lovullo said of the struggles.

What keeps Lovullo from being more concerned is the realization that he’s asked a lot of his relievers of late.

The three-game series in Colorado taxed them heavily. Against the Rays on Wednesday, they played 13 innings. It’s left them most nights without all their relievers available, as they required rest.

“I feel like once we get our feet on the ground and get everybody lined up the way we need to, we’re going to avoid some of those bumps in the road,” Lovullo said. “Our bullpen is an area of strength for us. We’ve just been mixing and matching over the past five or six games. I know that they’re doing all that they can but it’s to be expected. This game can be challenging when you miss spots and get behind hitters you pay for it. I think that’s where it’s caught up to them a little bit.”

Making a move

Following the game the team optioned Ildemaro Vargas to Triple-A Reno. While a corresponding move won’t be announced until Saturday it looks likely that catcher Alex Avila will be removed from the injured list, where he’s been since April 7 with a strained left quadriceps muscle.

Graduation

Pitching coach Mike Butcher was not at Friday night’s game so that he could attend the college graduation of one his children.

Bullpen coach Mike Fetters filled in for him.