CLEARWATER, Fla. - Zach Eflin had to step outside Frenchy's beachfront restaurant on Friday evening. His phone was buzzing, and a band was playing inside. The call was from Joe Jordan, the Phillies director of player development. The pitching prospect had no idea why Jordan was calling.

Jordan told Eflin he will start Monday for the Phillies when they travel south to Bradenton. The 20-year-old will face the Pittsburgh Pirates in his first game against major-league opposition. Eflin said he was "really, really excited." He went back into Frenchy's and finished his grouper sandwich.

"The fact they're giving me an opportunity to showcase what I have is just incredible," Eflin said. "It's an opportunity for me and the club to get to know each other better and see what I can do against big-league hitters."

Eflin sat in the stands Friday afternoon at Bright House Field when Aaron Nola, the organization's top pitching prospect, started against the New York Yankees. Eflin texted Nola afterward to say it was fun watching him strike out four batters in three scoreless innings.

He plans to talk with Nola about what to expect on Monday. Eflin, a righthander, will be the third Phillies prospect this week to pitch in a major-league spring training game. Severino Gonzalez pitched three scoreless innings Tuesday against the Atlanta Braves. Eflin said he still never expected to get a call.

"Never once did I think it would happen to me or anything," he said. "I didn't think since you got one, I should get one at all. Not at all."

Eflin joined the Phillies in December as part of the trade that sent Jimmy Rollins to the Los Angeles Dodgers. He made 24 starts last season with San Diego's high-A affiliate. Eflin finished his third professional season 10-7 with a 3.80 ERA. He struck out 93 batters and walked 31 in 128 innings. He throws a fastball that zips in the mid-90s, a slider, and a change-up.

"You're basically just watching how they compete," Phillies pitching coach Bob McClure said. ". . . How do they deal with it?

"You can kind of tell, 'Is the game speeding up for them? Is he still making pitches even though there's traffic [on the bases]?' . . . It takes a little while to kind of get your feet on the ground."

Baseball America regards Eflin as the Phillies' second-best pitching prospect. He will likely begin the season at double-A Reading, where he could join several other prospects in a loaded rotation.

Nola, Jesse Biddle, Tom Windle, and Ben Lively are candidates to join him in Reading when minor-league camp breaks next week. Biddle, Nola, and Eflin are former first-round picks. Windle, a lefthander, is the team's third-best pitching prospect, according to Baseball America. Lively, a righthander, is fourth.

Eflin has not yet been told where he will begin the season. That could be a good thing, he said.

"It's just an opportunity for me to grow and learn, especially against big-league hitters," he said of Monday's start. "I think the success I've had in my career has led me to be able to pitch at this point. I'm just really looking forward to it."

@matt_breen

Jake Kaplan contributed to this article.