The A’s could not have known ahead of time how this outing would turn out for Frankie Montas, but after giving him what they deemed as enough time to recover from the upper back tightness that prevented him from making his prior start, they were fairly certain he wouldn’t have any restrictions in his return to the mound.

The good news is that Montas' performance was not injury-related. But the outcome was suboptimal, and the A’s lost to the D-backs, 10-1, at Chase Field on Tuesday night.

• Box score

“It was just a rough day," Montas said. "I didn’t have it at all.”

Kole Calhoun led off the game with a double, and Montas never seemed to be able to settle in after that. The dagger in an opening frame that included three walks was Nick Ahmed’s three-run homer on an 86.6 mph splitter that hung over the plate.

Calhoun led off the second with a 431-foot homer to straightaway center, and five batters later, Montas’ outing -- the shortest start of his career -- was over.

Neither Montas nor manager Bob Melvin had any concerns that the pitcher’s poor performance was anything more than rust.

“He's just a little out of sync,” Melvin said. “You saw him spike some pitches in the dirt, and other ones hung up a little bit, and you're fine trying to find your arm slot. Maybe early on, you're a little bit tentative, but the velocity was there. It just ended up being a tough game for him.”

Montas said he had no lingering effects from the neck and back pain that sidelined him last week, but he acknowledged the brief layoff may have knocked him off-kilter a bit.

“I think my timing, my mechanics, were a little off today, and my release point was not right,” he said. “I think that was the problem today.”

Montas, whose scheduled start on Friday vs. the Giants was called off when he came down with the back ailment, threw a full bullpen session on Sunday and seemed ready for this outing. Only a week removed from being named the American League Player of the Week following two sterling starts, Montas reached mile markers in this outing he’d probably like to do without -- the homers were the first he’s allowed all season, and it’s only the fourth time in his career he’s allowed multiple homers in a outing. All told, he allowed nine runs in 1 2/3 innings in Arizona.

Between his two innings on the mound, Montas assured Melvin and pitching coach Scott Emerson that he felt fine physically and that he was able to go out for the second frame.

“Honestly, they were probably concerned about my neck, my upper back,” Montas said. “I told them that I felt good. It was just -- my timing was off.”

“Hopefully, the cobwebs are off now, and next time around, we see the guy that we've seen, for quite a while now,” Melvin said.

The A’s red-hot start has cooled a little as the season approaches the four-week mark. The effectiveness of the pitching has, so far, been split in August.

During their nine-game winning streak that opened the month, A’s pitchers allowed 19 runs for a 1.88 ERA. But in their past eight games, pitchers have given up 50 runs (49 earned), for a 6.21 ERA. Oakland is 4-4 over that stretch.

The club is also 16-8 on the season, which is good for first place in the American League West. They’ll open a two-game series with the D-backs on Wednesday with a 1 1/2-game lead on the Astros, the only other team in the division with a winning record.

Though they’re only 3 1/2 weeks in, given the oddities of the season, it’s not too early to scoreboard watch, is it?

“It's weird, especially with the new playoff format,” outfielder Stephen Piscotty said. “Obviously, we all want to win the division, but there's a lot more teams getting in this year, so there's a lot more going on that I don't think a lot of us fully understand.

“As we get closer, real close to the end, I think that's when you start looking around at other teams and seeing where you're stacking up. But for right now, just try to win. Win each game."