Selected by the Mariners in the 2010 First-Year Player Draft with the compensatory pick they received after the departure of free agent Adrian Beltre, Walker threw 126 2/3 innings last year for Double-A Jackson. Under the heaviest workload of his career, he went 7-10 after a dominant 4-1 start. It was a time of growth for Walker, then 19 and the youngest pitcher in the Southern League.
"I learned a lot last year about pitching and about myself, so it was a great experience for me," he said.
Walker, now 20, has a familiar face in Mariners' camp in 2012 first-rounder Mike Zunino, who caught for Walker in Jackson. Zunino, who ranks 23rd in MLB.com's Top 100, caught a bullpen session with Walker earlier this week, and he said the pitcher made good adjustments over the winter.
"His arm looks fresh now," Zunino said. "I know it was a long year for him last year, but his [bullpen session] looked great, and I think he's ready to get going again."
Pitching coach Carl Willis is excited about Walker's potential.
"He is a physical specimen," Willis said. "I mean, he really looks great and ready to go. And you know, it's his second Spring Training; I think that's huge.
"I expect him to compete for a spot on the club. He is still young from an experience standpoint, but you can't disregard the stuff that you see."
At the start of camp, Willis will examine how Walker handles the basics: pounding the strike zone, controlling his pitches and using his breaking balls effectively. Once the Cactus League games begin, Willis will also look for how Walker handles the mental side of pitching.
"It's not 40,000 people at Fenway Park, but it's a Major League game, Major League players, ESPN highlights," Willis said. "I mean, you have to learn how to deal with more of the outside factors than really the game itself, so we'll look how he handles that too."
It won't be the first time Walker has been on a big stage -- he got a taste of that when he played in the 2012 All-Star Futures Game at Kauffman Stadium in Kansas City, Mo.
"It was awesome, pitching in front of a big crowd in a Major League stadium," he said. "My family was there, so I thought it was pretty cool, being on national TV and stuff."
It may not be at an All-Star Game in Kansas City or in front of 40,000 at Fenway, but Walker will have a chance to show his stuff to the Spring Training crowds after Cactus League games begin Feb. 22.