The Red Sox acquired Mills, now 30, from the Royals in exchange for minor league pitcher Jacob Wallace on December 16, 2022. Boston was excited about his potential as a bullpen asset for 2023. With a pitching arsenal featuring a four-seam, sinker, and slider—and an arm angle similar to John Schreiber—one team official even believed Mills might possess superior skills.
Unfortunately, Mills suffered an injury during spring training and had to undergo Tommy John surgery in July 2023.
Over the past two summers, Mills has been at JetBlue Park in Fort Myers, dedicated to his recovery and rehab. The repetitive routine in the heat led him and fellow rehab players, including Michael Fulmer and some minor leaguers, to join a bowling league and participate in a miniature golf tournament to break up the monotony. “We made the best of it,” Mills said.
“Over here, we visited five or six different mini golf spots,” he explained on Friday at JetBlue Park. “We even had a full leader board, and I prepared weekly updates for the training staff and the other players. We wrapped it up with an event called the Masters at Pop Stroke—everyone dressed up and played 36 holes. It was a great time.”
Mills is now having a strong spring season, allowing just one run, two hits, and one walk while striking out six over 4⅔ innings in four outings.
“I’m excited,” he remarked. “I was traded here for a reason. I know what I’m capable of, and I’m ready to contribute to a team that’s poised to be a real contender. I plan to keep doing what I do best and trust my skills. If I get ample chances to help the team, that’s fantastic.”
Mills also complimented Fulmer, calling him “quite the bowler” and noting, “He even has his own bowling balls. There are some really sneaky good bowlers around here.”
However, Mills’ involvement in the bowling league took a backseat in July when he started a family. He and his wife welcomed a baby girl last summer, and having his family nearby made the long hours of rehab more bearable. “We actually had the baby here in July—it helped the time go by,” Mills added.
While there’s never a perfect time to be injured, being home full-time rather than traveling with the team turned out to be a silver lining. “It was perfect timing,” he said. “I was rehabbing, and after work I could go home. Knowing we’d be in one place all year was like a calm in the storm of my career.”
Although he stepped back from the bowling league to spend time with his family, he noted that his teammates really ran with it.
Throughout 2023, Mills remained on the 40-man roster—albeit on the 60-day injured list. After Boston non-tendered him on November 17, 2023, they signed him to a unique two-year minor league deal the very next day, which allowed him to rehab with the team and gear up for a 2025 return.
For Mills, it feels like ages since he last pitched; his most recent major league appearance was on September 3, 2022. “It’s been long summers here, but now that I’m back in the swing of things, it feels like old times, and that’s great,” he said.
He expressed being “pleasantly surprised” by his spring training performance. Reflecting on his pre-injury capabilities, he added, “I know my stuff played at the highest level before I got hurt. It’s tough taking two years off and expecting to return at the same or a higher level. I’m really pleased to see the results of all the hard work—I’m more consistent this spring than before, which shows what a year and a half of focused work can do.”
Mills has evolved from using three pitches to now employing four. He refers to his four-seam fastball as “his bread and butter.” Regarding his slider, he explained, “I adjusted the grip slightly to improve its consistency,” and he used Trackman data to fine-tune its shape.
“The same goes for my sinker—I changed the grip to get more consistent movement and shape,” Mills noted. “I also added a changeup, a pitch I’ve always tried to master. I’m finally comfortable throwing it against big league hitters, and I hope it becomes a key weapon against lefties this year.”
His four-seam fastball still sits in the 90-93 mph range, with occasional bursts of 94-95 mph. “They’d like to see me at 94-plus because it boosts everything else, but I’ve found that even at my current velocity, I’m recording outs and keeping hitters off-balance with the pitch’s deception,” he remarked.
Mills acknowledged that coming off an injury means he’ll face ups and downs. “I know I need to prove my consistency over a long stretch, and that’s ultimately up to the team. When my turn comes, I’m ready to go out and help,” he said.
He admitted he didn’t enter spring training with high expectations of making the Opening Day roster. “I came here to pitch well—to feel good and pitch well—and to remove the pressure of high expectations. Now that I’ve seen what I’m capable of, that would be amazing. There’s a lot that goes into it, so I just plan to focus day by day, take care of my body, and be ready when called upon.”
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