CHICAGO -- Zack Burdi has departed Arizona exactly once since arriving on Jan. 29, taking a break to catch a Golden Knights hockey game in Las Vegas.
Otherwise, it has been all about stringently following the throwing program, as the White Sox No. 26 pick in the 2016 Draft and No. 12 prospect per MLB Pipeline approaches the 10-month mark since his Tommy John surgery on July 27, 2017.
"I guess you could say I'm still very driven and encouraged by the process and learning a lot by kind of being on the sidelines this year," Burdi told MLB.com via phone from Glendale, Ariz. "You take a step back and look at your season last year, and you can nitpick stuff that kind of went over your head because of the daily grind of going to the field and playing. Just a constant routine.
"Now it's just taking advantage of this time off and trying to build up my body and getting into routines I can sustain throughout the year. When next season comes, just try to be at my peak level."
Burdi, 23, has been tabbed as the White Sox closer of the future since coming to Chicago via Louisville and Downers Grove, Ill. He had seven saves in nine chances for Triple-A Charlotte in 2017, along with 51 strikeouts over 33 1/3 innings, when the arm injury and ensuing surgery knocked him out.
Friday marked Burdi's fourth bullpen session of approximately 20 pitches off the mound at Camelback Ranch, and it was focused on fastballs, although he has incorporated sliders during warmups. Those lessons learned Burdi spoke of range from pitching mechanics to off-the-field preparation.
"I've really condensed my delivery, shortened my arm action," Burdi said. "I'm kind of getting away from that side-to-side and getting more over the ball and getting when my arm comes out of my glove, getting up higher and not dropping it down and having this big loop and being late on my ball.
"In the gym, I'm just really trying to work on stability and mobility, and then trying to get stronger, because it's kind of like an extended offseason for me. I have a lot of time to build up my body and kind of work on things that you can't really get to or maintain."
The original healthy return for Burdi centered upon Spring Training 2019. Burdi feels "awesome" and could throw with an affiliate during this season, but instructional league or Arizona Fall League action also remain possibilities if he is ready.
"It felt really good controlling the zone and commanding my pitches," Burdi said. "I'm not trying to blow away the catcher or trying to make anything too nasty. Just get the stability back on the slope and make sure everything feels right and fluid together."
"We knew the 2018 season, in terms of what he did, was more about just getting healthy," said general manager Rick Hahn. "The 2019 season was about returning to competitiveness. If he pitches in games this year, that's wonderful. He's building. He's doing a nice job with the rehab. He's worked hard. We'll see how he progresses."