CLEARWATER, Fla. -- The look from Casey Mize as his 0-2 pitch to Bryce Harper headed toward the right-field berm summed up his emotions Saturday. His head dropped before the two-run homer did.

It was Mize's hardest pitch of his outing, a 96.6 mph fastball according to Statcast. But it was over the plate to an MVP, who hit it out with a 109 mph exit velocity.

“[I] had him 0-2. Really, really nice plan that we’d kind of planned out,” Mize said. “Had him right where we felt like we wanted him, but I didn’t get the four-seamer up enough, left it over the heart of the plate and he smashed it.”

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Harper’s first-inning homer and Didi Gregorius’ third-inning grand slam accounted for all six runs off Mize during Saturday’s 9-3 loss to the Phillies at Baycare Ballpark. Three of the four runners on base reached on walks, raising Mize's total to nine walks against seven strikeouts in 6 1/3 innings this spring. He had the same walk total over 83 2/3 innings during his sophomore season at Auburn.

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It’s not the way the Tigers’ No. 2 prospect envisioned his bid for a rotation spot. It’s also not over, and he isn’t the only Tigers starting candidate struggling.

“Obviously, as a player, it’s frustrating when you give up six runs. So definitely, it sucks,” Mize said. “But at the end of the day, this is short term, and it’s not really going to affect my long term if I continue to trust my process and put quality work in.”

Somewhere in that process, Mize has to balance hitting the strike zone more consistently against getting hit.

“Learning experiences for him,” Detroit manager A.J. Hinch said, “but he’s going to get some work, and he’ll be back out there in five or six days. But obviously, execution -- not only within the strike zone but also purposeful -- is going to be important.”

Mize also has to balance working on his pitches against results that win a spot. Hinch doesn’t want his young pitchers to panic and lose focus, but he does want them to compete, rather than take a spot for granted.

“We can’t ride the roller coaster of emotion that comes with: When he does well, he’s on the team; when he doesn’t do well, he’s not on the team,” Hinch said. “I think we’re looking at a big picture with him. We’re also looking at seeing what he can do against Major League hitters today, to determine whether or not he’s going to break with us.”

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Mize’s strike-zone balance Saturday wavered from inning to inning, sometimes even batter to batter. He opened with a five-pitch walk to Andrew McCutchen, then a four-pitch strikeout of Rhys Hoskins with a called third strike on the corner.

Harper’s homer was the first Phillies swing that made contact. It came on Mize’s 12th pitch of the day.

“It’s funny, because [I threw] an 0-2 heater to Bryce and he hits a homer,” Mize said. “A week ago, I’m probably not throwing a strike. But today, I’m throwing a strike in that situation, where I can afford not to throw one.”

Mize’s next pitches induced a single and two groundouts to end the inning. He retired the bottom of Philadelphia's lineup in order in the second, including a 96-mph fastball to freeze Roman Quinn, but he found trouble again once the lineup reset in the third.

Mize had McCutchen in a 2-2 count but hung a sinker that McCutchen lined off the wall for a leadoff double. Mize had Hoskins and Harper in 0-2 counts before walking both; Harper took four consecutive pitches out of the zone after swinging and missing on back-to-back curveballs.

Until Saturday, Mize had gotten away with the walks, having not surrendered a hit while striking out four. But like Harper, Gregorius punished Mize for a pitch over the plate, this one a hanging splitter following two high fastballs.

“Just a lot of non-quality pitches,” Mize said.

Mize induced 11 swings-and-misses in 59 pitches, including a strikeout of Jean Segura to end his outing following the grand slam. The Phillies’ eight balls in play against him averaged 96.4 mph. The potential is there through the struggles, but Mize has to translate it.

“It’s always a continual development,” Hinch said. “If he makes the team or doesn’t make the team, his development is not over. He’s got a lot of work to do, to get to be the best version of himself, and we need to determine where that is.”