MINNEAPOLIS — Casey Mize wasn't smiling as he walked off the field after the sixth inning.

He is a tough competitor.

"Compete was probably the biggest word for the day," Mize said. "I was just trying to get outs with what I had."

He competed his way to completing a scoreless start of at least six innings for the first time in more than 1,100 days, and when the Detroit Tigers finished Sunday's 6-1 win over the Minnesota Twins, he recorded his first win in nearly 1,000 days.

The scoreless achievement hadn't happened since April 12, 2021, and the personal win hadn't happened since Aug. 24, 2021. Those dates were more than a year before Mize underwent elbow surgery and back surgery during the 2022 season.

Mize, who turns 26 on May 1, missed all of last season while rehabbing from the surgeries, but this season, he is finally back as a competitor on the mound. In four starts, Mize has a 2.95 ERA with six walks and 16 strikeouts across 21⅓ innings.

"It was a battle," Mize said of Sunday's outing, "but if I leave the game and there's a zero in the run column, it's hard not to be happy with that. I'm happy to compete and keep us in a chance to win, and that's what we did."

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Before Sunday's game, Mize shared a new detail about the back injury he dealt with throughout the first three seasons of his MLB career.

He suffered from pain along the sciatic nerve running down his left leg. It can happen when a herniated disk or bone spur in the spine presses against the nerve, and in some cases, it can feel like an electric shock.

"The issue was that I had was sciatic nerve pain down to my left foot, so I couldn't straighten my leg," Mize said. "When I would land, I couldn't straighten it or else it would shoot nerve pain down my leg. Physically, my body was saying, Stay out of these positions, it hurts, it's hurt like this for a while. Now I'm pain free, and it took me a while for my brain to recognize that and my body to follow suit, and now, I'm able to stick the leg in the ground and brace it really hard. That energy transfer is happening a lot better than when I wasn't able to do that in the past."

Mize previously described his back surgery — which occurred after Tommy John surgery to reconstruct the ulnar collateral ligament in his right elbow — as a life-changing procedure.

Back surgery led to new mechanics.

New mechanics created more fastball velocity with more ride.

An elite fastball is helping Mize succeed in compete mode.

"We did a lot of drill work and stuff after my body was healed," said Mize, who added 20 pounds — mostly muscle — in the long rehab process. "We did a lot of stuff in the weight room, a lot of dry work on the mound with med balls to repattern this stuff. I had to convince my brain, It's OK, it doesn't hurt, you can move this way. We did months and months of work on that, which was difficult. It took a lot of work, but I'm on the other side of that now."

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The new mechanics are highlighted by the lead leg block, essentially extending the knee after planting the foot. Pitchers who extend their knee more throw harder than pitchers who extend their knee less.

Let Mize explain.

"A lot of guys do it in different ways," Mize said. "If you watch mechanics, you'll see a guy who braces in the ground and literally it looks like he hyperextended his knee, and then you'll see, like (Tarik) Skubal doesn't. Skubs, he's got a bent knee, but he's just so strong that it's like he's absorbing the energy and sending it up, where that knee doesn't track forward. Bracing looks a lot different, but for me, it's in the ground and tracking forward."

The first three years of Mize's MLB career were plagued by the inability to perform the lead leg block because of the pain down his left leg from his back injury. Without that movement, he couldn't capture significant energy from the ground, and without that energy, he couldn't throw high-velocity fastballs.

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His fastball averaged 93.4 mph in 2022.

It's averaging 95.4 mph in 2024.

He has thrown 30 fastballs above 96.9 mph in just four starts, maxing out at 98.4 mph.

"I think about my fastball differently, but not the other stuff," Mize said. "In the past, 1-1 (count), 2-1 (count), here comes the slider because I don't have a good enough fastball in a fastball count to beat you. Now I feel like it's not always going to be a slider. I feel pretty confident, 2-0 (count), here's my best heater versus your best swing, let's see what happens. I feel better about that now. And I think it helps my other stuff play a little bit better."

A better fastball is the product of a career-changing back surgery followed by a significant mechanical adjustment. As a result, Mize is better equipped to compete — and win the competition — than ever before in his career.

He showed that in Sunday's win.

"It was kind of funny because Casey's line was awesome," manager A.J. Hinch said, "but it wasn't without a fight and a grind. ... He had to pitch through a little bit of duress, even though it feels like a guy who throws six scoreless was in cruise control. I'm proud of his effort because it wasn't as easy as the line is going to make it look."

Contact Evan Petzold at epetzold@freepress.com or follow him @EvanPetzold.

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This article originally appeared on Detroit Free Press: Detroit Tigers' Casey Mize: Back surgery has led to best version of me