How will Phillies ace Zack Wheeler fare in his season debut? Even he isn’t sure.

ATLANTA — When Zack Wheeler started along his road to recovery, he circled one date on the calendar.

“I wanted to [pitch] opening day,” he said Friday.

But nobody comes back in only six months from thoracic outlet syndrome. The Phillies ruled it out even before spring training. And once that was off the table, well, this weekend — in this city — seemed like as good a target as any.

It always comes back to Atlanta for Wheeler. He was born a few miles from where the Braves’ ballpark now stands. He grew up about 30 miles away. He made his major league debut here in June 2013 for the Mets. Got his first win in Atlanta, too.

» READ MORE: From 2021: The rise of Phillies' all-star ace Zack Wheeler

There isn’t a more apt setting, then, for Wheeler’s first start since the August weekend when he was diagnosed with a blood clot near his right shoulder, the byproduct of a vein that was compressed between his rib and collarbone.

But on the eve of his comeback — a sight for the sorest Phillies eyes amid the nine-game losing streak that they dragged into Friday night — the 35-year-old ace tried to downplay the significance of it all.

“Yes, it’s nice to come back, nice that I made it back,” Wheeler said before the Phillies opened a series against the division-leading Braves. “I’m grateful for that — and for my wife and kids and family and friends being there for me and helping me get through it. It’s been awesome,

“But, I mean, other than that, I’m here to pitch.”

As for how Wheeler will pitch, even he isn’t sure.

Wheeler made five starts in the minor leagues that the Phillies treated like a spring-training build-up. The results — 5.85 ERA, 19 hits, five walks, 23 strikeouts in 20 innings — didn’t matter as much as how Wheeler felt. By all accounts, he felt healthy.

But Wheeler’s fastball velocity wasn’t up to speed. After averaging 96.1 mph last season, he was mostly in the 91-93 mph range, scraping 94 mph.

It isn’t unusual. Peak velocity is the last thing to come back, according to pitchers who have returned from thoracic outlet syndrome. And Wheeler will turn 36 at the end of next month. Healthy pitchers tend to begin losing a tick or two of velocity in their mid-30s.

» READ MORE: What is Zack Wheeler facing in his return from surgery? We asked two pitchers who have done it.

Wheeler isn’t deluded by any of it.

“I don’t think I’m all the way there,” he said. “Definitely can say that, just being honest. I’ll be ready. But with my velo down just a little bit, you’ve got to pitch and hit your spots and move the ball around a little bit more. Maybe try to get some more swing and miss, but not necessarily over-try because that’s when you start getting into trouble.

“So, I think we just get in there [Saturday], see how it is, see how it’s going, and deviate one way or the other if we have to.”

Wheeler is better equipped to make those adjustments than he was early in his career. Back then, with the Mets and even in his first few years with the Phillies, he leaned on his fastball to overpower hitters.

But over the last few years, Wheeler added a splitter and sweeper, the slider variant that has become popular among pitchers. He’s better able to mix his pitches when he lacks his best fastball.

Wheeler often cites the beginning of the 2024 season, when his fastball averaged only 93.1 mph and 93.9 mph in back-to-back starts before climbing to its normal levels. He survived by using his other pitches.

“It’s definitely different,” Wheeler said. “It’s definitely harder. You don’t get as much swing and miss. You get foul balls. The first few [starts] may be different than what I’m used to, or what other people are used to. But hopefully I’ll get to where I want to be.”

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And if the fastball doesn’t fully return?

“It’s a thought, right?” Wheeler said. “It’s a thought. You want to be who you were because it makes pitching a lot easier. But at the same time, you can’t do anything about it necessarily. That’s why, between each start, you try to figure out, ‘Hey, what’s going on?’”

Said manager Rob Thomson: “If he’s commanding the baseball, that’s the key, really. He spun the ball really well in his rehab starts. It’s just fastball command came and went a little, I think, due to weather in some cases. I think he’s going to be fine.”

In any case, he’s still Zack Wheeler, among the best pitchers in baseball since 2020. And considering the Phillies haven’t had a starting pitcher complete seven innings yet this season, they couldn’t pick a better time to plug their erstwhile horse back into the rotation.

“He’s not going to be in midseason form. I’m not expecting that,” Thomson said. “But I think he’s going to compete and give us some innings, for sure.”

Wheeler will have to navigate his first start without J.T. Realmuto, his favorite catcher. Realmuto, sidelined by back spasms, returned to Philadelphia to get treatment in the team’s hyperbaric chamber. Thomson said Rafael Marchán will catch Wheeler and Aaron Nola on Saturday and Sunday, respectively, after Garrett Stubbs caught rookie Andrew Painter on Friday night. … Braves center fielder Michael Harris II was scratched from Friday night’s game with quadriceps tightness. … Wheeler will be opposed by Braves righty Bryce Elder (3-1, 1.50 ERA).

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In Trea Turner and Justin Crawford, the Phillies have two of baseball's fastest players at the top and bottom of their batting order. It's a baserunning coach's dream. Paco Figueroa sat down with "Phillies Extra" to discuss his philosophy on baserunning and how the Phillies might be able to leverage the elite speed of Turner and Crawford to boost an offense that has struggled to score runs early in the season. Watch here.

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Previous episodes: Gage Wood | Scott Boras | Brian Barber | Aaron Nola | Justin Crawford | Garrett Stubbs | Kyle Schwarber | Brad Keller | J.T.Realmuto | Orion Kerkering