CHICAGO -- A few times a week, DJ Herz would head to his backyard in North Carolina and step onto the portable wood mound that his dad constructed. The lefty would fire pitches into a nine-pocket net and record videos to send to the Cubs.

The Minor League campaign may have been lost to the pandemic, but Herz did not want to lose the feeling he had in his abbreviated Spring Training two seasons ago. So he applied the new changeup grip, fired baseballs into that net and repeated the process.

"That's all we could do," Herz said. "My big thing was making sure I stayed on top of it."

Speaking this week from Arizona, where Herz has been taking part in an offseason camp for Cubs prospects, he knows those isolated training days did pay dividends. After his breakout showing at two Class A levels in '21, both the Cubs (via the Vedie Himsl Award) and MLB Pipeline named Herz the organization's Minor League pitcher of the year.

Across 20 starts between Low-A Myrtle Beach and High-A South Bend last year, Herz racked up 131 strikeouts against 44 walks with a 3.31 ERA in 81 2/3 innings. Among all Minor League pitchers with at least 80 innings in '21, the left-hander ranked third in strikeout rate (40.4 percent), strikeouts per nine innings (14.4) and opponents' average (.159), opening up eyes along the way.

"I'm not shocked," Matt Dorey, the Cubs' vice president of player development, said in November. "We knew what kind of athlete and competitor he was. But the fact that the stuff has jumped this much, this fast, that's really a credit to him and how hard he's worked."

The timing of baseball's shutdown in March of 2020 could have threatened that developmental momentum for Herz.

When Herz -- an eighth-round pick in the 2019 MLB Draft -- arrived to Spring Training, the readings in the Cubs' pitch lab had everyone excited. The lefty said he was sitting at 94-95 mph at the time with encouraging data coming in on a spike-curve that remains a work in progress.

Beyond that, Herz finally found a changeup grip that felt right and had the potential to give his fastball a peripheral boost. After testing a few variations that yielded uninspiring results, Casey Jacobson, Chicago's coordinator of pitching development, had Herz try a "Vulcan" changeup, which requires splitting the middle and ring fingers apart.

"The first throw, it was low-and-away and it had sink, and it had run," Herz said. "And it was really good off my fastball for tunneling. Casey was like, 'That's the one,' and we stuck with that. That's why I was determined over 2020, like, 'This pitch could be really huge for me.'"

During the shutdown period, Dorey noted that the Cubs sent "a really extensive nutrition, strength and conditioning plan" for Herz to follow at home in Fayetteville, N.C. The lefty stuck to a regular throwing program, but also teamed with a former coach to check the boxes on the Cubs' weekly list.

"The [shutdown] was bad for a lot of people," Herz said. "But I think it was a blessing in disguise for me. I was 19 still, and I'm a late bloomer, so my body was still catching up."

Dorey joked that Herz "bounces off the walls" if he is not doing something, given his past as a football, basketball and baseball star for Terry Sanford High School. Herz said, however, that narrowing his focus to one sport since signing with Chicago has actually been beneficial. He no longer feels pulled in so many directions.

When Herz arrived to Spring Training ahead of the '21 season, Dorey and the Cubs' player development staff could see a difference.

"He really bought into it," Dorey said. "He's a young kid that wants to go play hoops and run around and do fun stuff, but he was really committed to that plan. And without losing flexibility or athleticism -- because that's probably one of his most exciting characteristics and traits -- he did, he came in a lot more physical. The ball was flying out of his hand."

In those mound workouts in his backyard, Herz did not have the ability to take regular readings on his pitches. He was eager to see the data in the pitch lab. There was still work to do on the curveball, and Herz said it improved as the season wore on, but the new offspeed offering "was money."

"The changeup was way better than anybody expected it to be," Herz said.

And during the season?

"His changeup was disgusting at times," added Dorey.

Fresh off turning 21, Herz is currently ranked 13th on MLB Pipeline's Top 30 Cubs prospects list. The big leagues are still potentially a few seasons away, but he looks around the camp in Arizona and sees the makings of a promising future for a Cubs team facing a transitional phase.

"We all talk about that," Herz said. "Anybody that says anything, it's like, 'Man, just give the Cubs some time.' We're about to be really good. We've got the guys to do it, and you can see it. You've just got to be a little patient."