Kyle Muller’s first big-league outing was one that he’ll likely want to forget.

Muller, 23, allowed two earned runs, picked up a strikeout and didn’t walk anyone in his lone fifth inning. Though he allowed two runs, he had great command of his pitches, with 21 of his 25 pitches being strikes.

“His breaking ball and slider looked really good tonight,” starting pitcher Ian Anderson said of Muller. “Just the crispness and putting guys away is tougher up here. Even I had trouble tonight getting guys to two strikes.”

The Braves’ top left-handed prospect, Muller was brought on for Anderson with a 4-3 deficit. Anderson allowed two runs in the first frame before settling down for the next two innings. In his 14th start this season, Anderson allowed four runs off of seven hits and a walk, while striking out five. Four innings pitched matches his season-low.

Manager Brian Snitker agreed with Anderson that the 23-year-old prospect was a little amped up and expects him to calm down as he gets more appearances.

“I would have been (amped up) if I was him,” Snitker said definitively. “We had an off-day, and we’re getting stretched pretty thin. We have a big run ahead of us, too. Even the one inning he gave us helped them out today.”

After Muller’s inning followed by a three-run Dansby Swanson home run to tie the score at 6-6, LHP Tyler Matzek worked a clean three-up, three-down inning with a strikeout to keep it even.

That’s where, for the most part, the good performance from the Braves’ bullpen ended.

Right-hander Shane Greene entered in the top of the seventh and loaded the bases with two walks.

“The two walks hurt,” Snitker said. “You get in the last third of a one-run game and you start walking guys, things aren’t going to end well. Stuff was good even after the double, but you can’t walk guys.”

The walks were costly for the home team. A.J. Minter came in for the final one-third of an inning and surrendered a Christian Arroyo grand slam to give Boston a 10-7 lead.

Josh Tomlin and Will Smith came on in the eighth and ninth innings, not allowing a base runner as their club was only able to add one run to cut the final score to 10-8. It’s back-to-back nights the Braves allowed 10 runs to the Red Sox.

But for the Braves’ most recent promotion, the sense around the ballclub is that he’ll be here for a while.

“His stuff is great,” Anderson said of Muller. “It’s not easy for the guys he had to come in and face in his debut, a couple balls that came down the line that here and there could have gone foul. Once he settles in, I expect good things from him.”