PITTSBURGH -- The Pirates have signed half of their 2020 Draft class after announcing the signing of right-hander Jack Hartman on Monday afternoon.

Hartman, 21, was the Pirates’ fourth-round selection (108th overall) in this year’s Draft. He joins first-rounder Nick Gonzales and fifth-rounder Logan Hofmann, who also signed with the Bucs over the last week. Pittsburgh expects to sign all six of its picks but has yet to announce deals with right-handers Carmen Mlodzinski, Jared Jones and Nick Garcia.

Hartman went 1-0 with four saves, a 3.00 ERA and 22 strikeouts in 10 relief appearances this spring for Appalachian State University. The 6-foot-3, 205-pound reliever received a $60,000 bonus, MLB.com’s Jim Callis reported, well below the 108th pick’s slot value of $538,200.

• Pirates Draft Tracker: Every 2020 pick

“Jack hasn’t been pitching for very long but already shows very promising stuff with a fastball/slider combination that we believe has a chance to be very effective at the professional level,” Pirates general manager Ben Cherington said in a statement. “He’s a strong, physical pitcher with strong character and work ethic. We look forward to working with Jack in a Pirates uniform.”

Hartman bounced from Tallahassee (Fla.) Community College in 2017 to the College of Central Florida in '18, where he made 15 relief appearances while hitting .310 in 25 games as an infielder. He moved to the mound as a junior at Appalachian State, where he put together a 4.98 ERA while striking out 26 in 21 2/3 innings over 20 games.

Hartman took a step forward this spring, with a fastball that touched 97 mph, and Pirates area scouting supervisor Jerry Jordan was able to watch him pitch in person before his senior season was cut short by the coronavirus pandemic.

In an essay for Appalachian State’s website, Hartman wrote that he went to the Florida Baseball Ranch last summer to improve his mobility, stability and movement patterns. He spent more time tweaking his delivery and pitch mix during the fall and spring, and he was able to study Rapsodo data to better understand what made him most effective.

“For the teams out there, I have a young arm and a high ceiling,” Hartman wrote. “Mentally, I have so many more tiers to reach, and I feel like the mental side of the game is what makes a big leaguer. If I can continue to progress on both sides, the mental aspect and the physical aspect, I feel like the sky is the limit for me. I’m continually making adjustments and adapting and I’m open to learning.”