PEORIA, Ariz. -- For all his dominance this spring, Padres prospect Chris Paddack was destined to come down to earth at some point. Surprisingly, his first spring speed bump came Tuesday against Mariners Minor Leaguers -- though the 23-year-old right-hander remains a strong favorite for the season-opening rotation.

Paddack threw 75 pitches in a prospects game at Peoria Stadium, allowing four runs on five hits over 4 2/3 innings. Still, aside from a small handful of mistakes, Paddack was very good, striking out eight and getting regular swings and misses with all three of his pitches.

Paddack gave up a two-run homer in the fifth inning on a hanging breaking ball, but he was otherwise sharp. The two runs he allowed in the first came courtesy of some rough batted-ball luck on three hits.

Against big league hitters, Paddack has been dominant this spring, posting a 2.13 ERA and a 37-percent strikeout rate in four Cactus League outings. In a very young rotation with three spots still available, he's made the loudest case.

"I'm going out there each and every day, showing them I belong, showing them that I'm ready," said Paddack, the Padres' No. 5 prospect per MLB Pipeline. "We have a lot of guys in that clubhouse still that are competing for that job. Whoever it is ... it's going to be a fun year, and I hope I'm a part of it. But that's something I can't control."

Paddack seemed to be emphasizing his curveball on Tuesday. His fastball is excellent, his changeup is elite and his command with both offerings is as good as any pitcher in the Minor Leagues. His curveball, meanwhile, remains a work in progress.

The first three times Paddack threw it in the second inning, he got swings and misses. It was sharp early, but it regressed a bit toward the end of the outing, when Mariners prospect Jake Anchia crushed one into the bullpen.

Afterward, Paddack indicated he was upset with himself for not carrying his Cactus League intensity into the exhibition.

“I wish I would've approached it a little differently,” Paddack said. “The mind is a really strong thing. If you change your game plan, this game will humble you. I wish I would have done a better job of telling myself there are nine Mike Trouts out there.”

Reading between the lines, it still seems very likely that Paddack is headed for the rotation. He was scheduled to start Monday, but that outing was pushed to Tuesday. Why?

"It was just the reality of making determinations on how our rotation was going to probably set up," Padres manager Andy Green said.

That would seem to indicate that Paddack is very much in the team's pitching plans, but Green wouldn't commit to saying so.

Whatever the reason for the late change, it now seems highly unlikely that Paddack makes an historic start on March 28. He could have become just the fifth pitcher in history to debut as an Opening Day starter, but he's no longer lined up for that date.

"Now that it's nine days away, the adrenaline is starting to rush a little bit," Paddack said. "Family's asking me a million questions, 'When? Where? What time?' I don't really know those questions, or those answers. But we still have a lot of work to be done."

Paddack will have his innings monitored closely this season. He threw only 90 last year in his return from Tommy John surgery, and the Padres aren't going to give him anything close to a full big league workload this year.

With that in mind, it might make more sense for Paddack to be aligned at the back of the rotation, where the Padres could use their off-days to give him rest. During the season, it's likely Paddack has a few starts skipped to keep him fresh.

"We'll set our rotation in a way that prioritizes health as much as it does winning," Green said.

Although Paddack has yet to pitch a big league inning, he's done little to disprove the notion he's one of San Diego's five best starting pitchers right now. If that's the case, it's hard to envision the Padres using up his limited 2019 innings on Minor League starts.

Right now, Eric Lauer and Joey Lucchesi are the only Padres who have secured their rotation places. The other contenders aren’t much more experienced than Paddack, and it’s become clear he’s a heavy favorite.

"We love what he's done," Green said. "We're optimistic about his future. He's in strong consideration to be on the team. There's really not much more he could do in camp. He's made a great impression."