The Spencer Howard era will begin Sunday.

After days of dropping hints but holding off on an announcement, the Phillies have informed their top pitching prospect that he will be called up from the satellite camp in Lehigh Valley to start one of the seven-inning games in Sunday’s doubleheader against the Atlanta Braves at Citizens Bank Park, according to a source familiar with the situation.

Howard’s first major-league start has been anticipated since the final month of last season and represents as ballyhooed a debut for a homegrown Phillies pitcher since Aaron Nola in 2015 and perhaps even Cole Hamels in 2006.

The Phillies needed to expand the rotation this weekend after Zack Wheeler and Nola started Wednesday’s doubleheader against the New York Yankees. Now that Howard is here, he figures to stay, given the likelihood that the team will require a sixth starter to help cover the half-dozen doubleheaders left on the schedule.

Before the Phillies call up Howard, they will need to create a spot on the 40-man roster, which might account for why they have not yet trumpeted the 24-year-old right-hander’s promotion.

Make no mistake, though: Howard’s arrival marks a big day for the organization.

“He’s going to be good. He has good stuff,” third baseman Jean Segura said this week. “I faced him a couple times in summer camp. His fastball is electric, especially against righties. He kind of jumps at you. Best of luck to the guy and happy to have a guy like that.”

Said second baseman Scott Kingery: “I think there’s excitement for everybody. His stuff’s electric. I faced him a couple times. Didn’t turn out well for me. He’s got good stuff, and I think he’s someone that can help the team.”

Howard might have broken training camp on the active roster if not for the Phillies’ desire to keep him in the minors for at least the first six days of the season to preserve six full years of club control. By delaying Howard’s major-league debut, the Phillies assured that he isn’t eligible for free agency until after the 2026 season.

But manager Joe Girardi and pitching coach Bryan Price scarcely concealed their enthusiasm about Howard during training camp, especially because the concerns from spring training about managing his workload after a shoulder strain limited him to 71 innings in the minors last season had vanished. If anything, the Phillies want to be sure Howard throws enough this season to be ready for next year.

“If this kid is the guy we think he is -- and we do -- then he’s going to have a really nice future in Philadelphia,” Price said a few weeks ago. “But at some point in time, he’s going to have to develop a workload. I would really hope and expect to see him pitching here, if not on opening day then in some point in time, because he really needs the work and I think he’s ready to compete at this level.”

Howard was the Phillies’ second-round pick (45th overall) in the 2017 draft. He burst on the scene by throwing a no-hitter in a playoff game for single-A Lakewood in 2018 and posted a 2.03 ERA in 15 starts between four minor-league levels last season.

In addition to an upper-90s fastball, Howard also throws a changeup, slider and curveball. The changeup might be his best offspeed pitch because he throws it from the same slot as the fastball but at least 15 mph slower.

“He’s got a delivery where his front arm, lead arm, kind of comes over the top, way up in the air, and then kind of just pulls it down,” Kingery said. “The ball gets on you really quick, has good ride. He’s got some nasty offspeed stuff. If the command’s there, his stuff is really good.”

Said Price: “We know that he’d be a top-end prospect in any organization because he has power, he throws strikes, he’s athletic, he has a really, really good changeup and breaking ball. The key component there is [quality] stuff with strikes, stuff with command. The sky is the limit.”

The journey will begin Sunday.