"I definitely got rejuvenated," he admitted. "I was joking around with the coaches and stuff that I got lulled to sleep pitching in Tampa all year. When I got promoted [to Trenton] I took it as a chance to prove myself and tried to capitalize on it."
Hidden behind his pedestrian numbers in Tampa were some real improvements. His 94 mph fastball improved a couple of ticks, his already great curveball also added some power, and he began introducing a brand new cutter that he had been working on behind the scenes.
"We talked about it in the first half of the season that maybe we were going to introduce it after the All Star break but ever since before the All Star break I'd mess around with it while playing catch and just get the feel for it," he said.
"All of the sudden in one game they said 'why don't you go out there and try it'. I threw it a couple of times and it was decent, but I kept progressively throwing it more everyday, throw it more in my sides [bullpen sessions] and a few more times in games.
"Maybe a couple of starts before I got bumped up [to Trenton] I was throwing it at least 15 times [per game] and the more I threw it, it just got better and better. I had one game in Double-A where I threw it 25 times and had 20 strikes. It was unhittable that game, it was awesome."
Always known for his knockout curveball, despite the fact that his breaking ball was even harder and sharper in 2013, Mitchell found himself going to the cutter for the big strikeout more often than his curveball, that's how much confidence he had begun to have with his newfound pitch.
"In Double-A I had a better feel for my cutter than I did my curveball so I was going to that as my out-pitch, especially to lefties," he revealed.
"You can it use it a lot more than I thought you could. It's really effective if you can throw it for strikes."
He had been throwing it for strikes consistently too and it was one of the big reasons why, despite amassing a career-high 145 innings and being a minor league veteran, he was invited to Instructs once again this offseason.
Mitchell was sent to Instructional League with one purpose in mind -- to master the cutter even more.
"I like the fact that I pitched at Instructs and showed that I can get guys out without my best pitch. I was only throwing fastball and cutter, and I was still effective. I was still getting outs, still getting strikeouts.
"To see that I could pitch with just two pitches and not even use my best pitch was really a big confidence booster for me. The cutter, when it's on, it's really, really good."
He has already put his disappointing statistical showing in Tampa behind him and has been re-energized by his improved arsenal and resulting late-season performance, and he believes he is only going to get better going forward, in part due to his 90-93 mph cutter.
"I feel at Double-A that I showed that I can pitch there, that I belong there. I'm confident. My plan is to go back, start just like I finished the year, and things will get better from there," he concluded.