Walker, who was immediately inserted into the lineup, didn't wait long to show the O's what he can do, doubling for his first Major League hit in the seventh inning of Baltimore's 6-1 win.
"There are so many things you get to have a good seat for. I hope it's the first of many," Showalter said of Walker, who was named the organization's Minor League Player of the Year. "We'll see. I can't imagine what was going through his head tonight. He hit it pretty well.
"I'd like to have been a fly on the wall when he saw the lineup go up. I was happy for him. That was cool. [He] made a good pick on a short hop."
The defensive compliment was just as important regarding Walker, who hit 26 home runs in the Minors this season but has been criticized for his defense at first base. Improving in that realm has been a priority this season.
"That was always a part of the game that I always wanted to work on and get a lot better at," he said. "I really tried to bear down this year and focus on my defense. ... I really wanted to not be a liability in the field."
Walker, who had around 10 family members and friends in attendance, said he'd send the ball for his first hit back home and didn't think the promotion had sunk in quite yet.
"It's awesome," he said of being a part of the AL East champs. "It's a lot of fun. A great group of guys to be around, and a lot of guys who really understand the game and a lot of stuff I can learn from."
Walker began the season at Double-A Bowie and earned a promotion after slashing .301/.367/.516 with 20 homers in 95 games. He played the final 44 games for Triple-A Norfolk and posted a .259/.335/.428 slash line with six home runs.
Walker's addition gives the Orioles a true backup first baseman. With Chris Davis suspended, Steve Pearce has started at first base full time. Kelly Johnson can also play first, but he has frequently started at third base since arriving in a trade with the Red Sox on Aug. 30.
With the division title locked up, Showalter can begin to take caution -- Nick Markakis received his third day off of the entire season Wednesday -- and that could mean giving Pearce days off. With Davis suspended, Walker is next in line.
"[We] don't want to get to the end of this season, and then all of a sudden an injury you weren't counting on pops up," Showalter said. "Basically, a guy who's an option has been down getting a few at-bats against instructional league pitching. This is a better place for it."