TORONTO -- Marcus Stroman has been the picture of consistency over an inconsistent season for the Blue Jays.

That is, until Friday night, when the 28-year-old right-hander allowed a season-high six earned runs -- five in the fourth inning -- on seven hits with two walks and four strikeouts, finishing 5 2/3 innings in the 8-2 loss to the D-backs to open the three-game Interleague series at Rogers Centre.

“They hit some good pitches, to be honest,” Stroman said. “[Kevin] Cron put a really good swing on an inside sinker that was probably four inches off the plate, and [Christian] Walker hit a cutter down pretty good. So they just beat me in that inning.”

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Two home runs accounted for two-thirds of Stroman’s run total, on a night when the American League leader in keeping the ball on the ground uncharacteristically allowed it up in the air. Entering Friday’s game, his 58.1 percent ground-ball rate was third among all pitchers.

“Honestly, I didn’t see that one coming because he was doing so well,” Blue Jays manager Charlie Montoyo said. “In that inning, [he left a] couple of balls up in the zone and they took advantage of it.”

In the series opener, the visitors hit the ball on the ground only 36.8 percent of the time. Among Arizona’s 19 batted balls off Stroman, seven were fly balls, four were line drives, one was popped up and seven were ground balls.

“That’s why it was weird, because he was getting all those ground balls early in the game,” Montoyo said. “Then that one inning he pitched up in the zone and they did a good job hitting him. He’s not that easy to hit and [you have to give them] credit for taking advantage of the ball being out of the zone in that inning.”

Toronto’s Opening Day starter entered Friday’s matchup as one of only 10 qualifying Major League starters with an ERA under 3.00 -- 2.84 before the outing, and 3.31 when all was said and done -- and he was the lone pitcher among the group with a losing record. Not including Friday, the Blue Jays averaged 3.38 runs of support with the righty on the mound, the seventh-lowest count in the Majors.

The start for Stroman was a stark contrast to that of his counterpart Merrill Kelly, who allowed one run -- a solo homer for Teoscar Hernández in the fifth -- on three hits with two walks and three strikeouts. Toronto’s foe was a familiar one for Montoyo, whose fondest memory of Kelly is that the right-hander helped him to an International League title in 2013.

“I wasn’t happy to see that,” Toronto’s manager said. “He was really good. [He had the] heat, but he threw strikes, he kept us off balance and he did a good job.”