Phillies ace Wheeler undergoes surgery to remove blood clot, but his return timeline remains uncertain.

Philadelphia Phillies ace Zack Wheeler had a successful thrombectomy today at Thomas Jefferson University Hospital in Philadelphia to remove a blood clot from his right arm.

The operation was carried out by Dr. Paul DiMuzio. Just two days prior, Wheeler was put on the 15-day injured list on Sunday because of the blood clot. His potential return date and next steps for this season remain unclear.

“We don’t know,” Phillies manager Rob Thomson said before the team’s series opener against the Mariners. “Until we get more information, we just can’t say.”

Right now, all attention is focused on Wheeler’s health and well-being.

“A lot of people are asking me about our pitching staff and the team, but honestly, my mind is on him,” Thomson said. “Like I said a few days ago, this isn’t a hamstring or a calf. This is real. This is life.”

“So my thoughts are with him and his family. Hopefully everything goes well—and so far, so good.”

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It’s been a whirlwind few weeks for Wheeler.

The veteran right-hander spent most of this season fiercely competing for the National League Cy Young Award. On July 6, he threw a complete-game one-hitter with 12 strikeouts against the Reds, making his chances of winning his first Cy Young honor seem higher than ever.

But after that outing, Wheeler wasn’t quite the same. Over his next six starts, he posted a 4.54 ERA, including a delayed start after feeling some shoulder soreness following his August 2 appearance against the Tigers.

Wheeler made two more starts after that—one on August 10 in Arlington, and another on Saturday in Washington. Although he said he felt better physically during those games, his velocity noticeably dipped against the Rangers. It improved against the Nationals, but was still below his season average.

“After the right shoulder soreness, Zack had been feeling better,” Phillies head athletic trainer Paul Buchheit said when Wheeler was placed on the injured list Saturday. “But on Friday, some symptoms changed. The doctors did a great job diagnosing and speeding up the process Saturday morning.”

Wheeler underwent further tests today and ultimately had surgery. According to Thomson, “the blood clot was cleared out.”

“He’s the heart of this team, the heart of our pitching staff,” said Matt Strahm, whose locker is next to Wheeler’s in the home clubhouse. “You never want to see something like this happen.”

However, the main concern is off the field right now.

Earlier in June, Wheeler spent a few days on paternity leave after his wife Dominique gave birth to their fourth child.

“First and foremost, he’s a father and his family comes first,” Strahm said. “That’s what we’re most worried about.”

As for baseball, Wheeler’s outlook is uncertain for now.

Thomson said today the team will stick with a five-man rotation for now, consisting of Cristopher Sánchez, Ranger Suárez, Jesús Luzardo, Aaron Nola, and Taijuan Walker.

“Yes, that’s the plan for now,” Thomson said. “I think we’re in a pretty good spot, at least for the time being.”

The most obvious replacement could be Andrew Painter—the team’s top prospect and the second-ranked pitching prospect in all of baseball. Painter has a 5.31 ERA over 17 starts at Triple-A Lehigh Valley this season.

Painter seemed certain to get called up earlier this season, but his unexpected struggles in recent weeks have made that less of a guarantee. Now, with Wheeler sidelined, the Phillies may be inclined to give Painter at least a taste of the majors, perhaps to utilize a six-man rotation.

This would give the rest of the rotation some much-needed extra rest. Nola just returned Monday and struggled after missing three months with a right ankle sprain. Suárez also had a rough outing before his start Tuesday. Sánchez is on pace to set a career high in innings for a second straight season, and Luzardo has thrown more than double his innings from last year.

That’s why the Phillies planned to use a six-man rotation after Nola’s return.

Wheeler’s absence changes that plan, but Thomson doesn’t want it to affect anything else.

“Like I told everyone, ‘Just be yourself. That’s all you can do. Don’t try to be anybody else,’” Thomson said. “Because they’re already good enough as they are.”