The lanky right-hander couldn't stay with the team during Thursday's game since he won't be on the 25-man roster until the Mariners create an opening Friday. But Walker, who turned 21 two weeks ago, soaked in the stadium and visiting clubhouse and got an early opportunity to picture what it's going to feel like for his first big-league start.
"I couldn't help but smile," Walker said of his first steps out onto the Minute Maid turf. "It's a nice park, too. I'm excited to have a big crowd in there and pitch in a big league stadium. But it's really going to hit me when I'm the mound tomorrow right before my first pitch."
Walker was the Mariners' first selection in the 2010 Draft as a supplemental first-round selection (43rd overall) out of Yucaipa High School in California. And while he's been on the fast track, that journey has seemed slow at times for the youngster.
"I've been working hard, especially this year," Walker said. "Getting sent back down to Double-A [Jackson], I knew I had a lot of stuff to work on. So, I've been trying to go out there every day with a purpose, with something new to work on. It's been going good for me. This year has been going well. Just to finally get the call up, it feels like all the hard work I've put in is finally paying off."
The 6-foot-4, 210-pound Walker is regarded as one of the premier young right-handers in the game, having pitched in the past two All-Star Futures Games and been listed as the Mariners No. 1 prospect and the No. 4 overall prospect in baseball by MLB.com.
Walker went 7-10 with a 4.69 ERA in 25 starts last year for Jackson and was 4-7 with a 2.46 ERA in 14 starts for Jackson this season before getting promoted to Triple-A Tacoma, where he went 5-3 with a 3.61 ERA in 11 games.
In 141 1/3 innings this season, Walker has 160 strikeouts and 57 walks with a 1.196 WHIP. He was the youngest player in the Pacific Coast League this year and will be the fifth-youngest player in Mariners history to make his debut as a starting pitcher at 21 years and 17 days.
Mariners general manager Jack Zduriencik has set about a 160-inning limit for Walker this season, which means he'll likely only start about three games with Seattle before being shut down. But he's not worrying about that right now.
"I'm just going to go out there and take it day by day, one start at a time," he said. "Whenever they decide to shut me down, they will. But as of right now, I'm going to prepare like I'm going to pitch the rest of the season."
Zduriencik said the decision to call up Walker now was to help "set the tone for Spring Training next year," but he declined to get specific on how much the youngster will throw after being used for 126 2/3 innings last year.
"We are going to be careful," Zduriencik said. "We aren't going to do anything crazy with Taijuan. I think the biggest factor is that he's going to get experience pitching up here. And even if it's short-lived and short innings -- a smaller sample than we might do with someone else -- that's the important factor. He's going to get his feet wet. He's going to understand what it's like to be on a big league mound and have a big league club behind him and the experience of being in a big league ballpark. I think all those things are a positive for him."
When Walker found out he was getting promoted on Wednesday, he immediately called his mom in California.
"She'd already found out through Twitter," Walker said, grinning. "She's always on Twitter, really active. So it wasn't much of a surprise when I called her, but it was still exciting. We face-timed and my brother and sister were there. I got on the phone and they just started screaming. It was awesome."