PEORIA, Ariz. -- When new Mariners pitching coach Pete Woodworth met promising prospect Justus Sheffield last year, it wasn’t in the best of circumstances.

Sheffield, the key piece in Seattle’s trade with the Yankees for James Paxton, had struggled badly in Triple-A Tacoma and been sent down to Double-A Arkansas to solve his issues. Woodworth, the young pitching coach for Arkansas, wasn’t sure what to expect.

“When guys get demoted, there’s usually a couple days they need to decompress and swallow what has just happened,” Woodworth said. “Sheffield showed up the first day and was so excited to get to work. As soon as he left the office after the first meeting, me and the manager looked at each other and said, ‘That is not what we were expecting.’”

Instead of a wounded prima donna, Sheffield came in as a hungry athlete looking for answers. Woodworth quickly discovered that what the 23-year-old needed most was a chance to rediscover his confidence.

And therein lies one of Woodworth’s strengths: the ability to connect with pitchers and reinforce their positive traits. In Sheffield, he had the perfect combination of a talented athlete with a desire to get better.

“He came in with the right mindset and immediately jumped into the culture we had there,” Woodworth said. “Obviously he’d been around these guys in Spring Training and him and Justin [Dunn] had a good relationship, but he clicked with the other starters and the entire team. Within two hours, he was a Traveler forever.”

“Most of his work was on the mental side. We didn’t do a ton physically. He’s good. He’s talented. He has elite stuff that comes out of his hand. Most of it was just getting him back to knowing who he was, getting confident and throwing his stuff over the plate.”

After going 2-6 with a 6.87 ERA in Tacoma and giving up 41 walks in 48 innings as he tried to nibble on the edges in the homer-happy Pacific Coast League, Sheffield quickly went 2-0 with a 1.00 ERA and no homers in 27 innings over his first four starts with Arkansas, and was 5-3 with a 2.19 ERA in 12 outings when he got the call up to Seattle in late August.

While he allowed a 5.45 ERA in seven starts over the final five weeks, Sheffield showed enough to convince the Mariners he belongs in their rotation this year. While fast-rising prospects like Jarred Kelenic, Julio Rodriguez and Logan Gilbert are drawing much of the attention, it is Sheffield -- now ranked as Seattle’s No. 9 prospect by MLB Pipeline -- who may be the most-important rookie this coming season as the Mariners begin piecing together their future rotation.

Sheffield knows this is a proving year for him, as the Indians’ 2014 first-round MLB Draft pick finally gets a full-time shot at a big league starting job.

“For sure,” he said. “I feel like every year is a step forward, but [even more so] this year. I’m looking forward to going out there and competing and changing this thing around and moving forward.”

Woodworth says that demotion to Double-A might have been the perfect tonic for the talented southpaw.

“His first bullpen we watched was like, ‘What? How did this guy not get people out in Tacoma?’” Woodworth said. “I wasn’t there, but those stories happened quite often in the PCL last year. But I’m kind of excited it happened for him, the adversity he went through and really learning how to deal with that. Which is something he and a lot of guys don’t really deal with early in their careers. He had a quick path to the big leagues, so I’m glad it happened to him. He is as well. He learned a lot through that process.”

What exactly did Sheffield discover?

“That I’m a fighter,” said the youngster from Tullahoma, Tenn. “I’ll continue to fight. I’m never going to back down from any challenge or obstacle that’s in my way. Baseball is a game of failure and I understand that. Moving forward, I just have to be able to get past those bad times and live for the highs.”

He’ll get plenty of opportunities for that this season as part of the rotation of the rebuilding Mariners. Only this time, he’ll have Woodworth at his side from start to finish.