Montero arrived in Seattle from Memphis, Tenn., on Thursday in time to suit up for the 7:10 p.m. PT series finale against the Yankees at Safeco Field, though the 24-year-old was not in manager Lloyd McClendon's starting lineup against right-handed rookie Chase Whitley.
McClendon said Montero will play primarily against left-handed pitchers, mostly at designated hitter, though there's an outside chance he might see some time at first base.
Montero was hitting .270 with 15 doubles, one triple, eight home runs and 40 RBIs in 59 games with Tacoma, with a .465 slugging percentage and .800 OPS, and said he learned from his experience after failing to make the Mariners' roster in Spring Training.
"It's tough. It's Triple-A and there are a lot of veteran guys there pitching," he said. "Sometimes it's a little tough, but sometimes you've got a good couple games. I feel great to be here, I feel like I earned it, I feel like I learned something. Now I want to be here forever."
What did he learn?
"The biggest thing for me was how valuable it is to be in the big leagues, how good it is to be in the big leagues," said the youngster. "I have to respect the game, I have to do the best to be here all my life, and to help the team to win."
While Saunders is an outfielder, the Mariners have more of a need for a designated hitter at this point, as they've been operating without a full-time DH since Corey Hart went on the 15-day disabled list on May 19 with a strained hamstring.
The Mariners have been going with an extra outfielder for the past two weeks since recalling Endy Chavez from Tacoma. Even with Saunders sidelined, they still have five outfielders in Dustin Ackley, James Jones, Cole Gillespie, Stefen Romero and Chavez.
Gillespie has been used at DH the past two games, and Romero and Ackley have also taken turns there, as has backup catcher John Buck. But Gillespie, Romero and Chavez likely will split time in right field on a regular basis while Saunders is sidelined, and Montero provides a right-handed bat to a lefty-heavy lineup.
"I think he's trying to get things back together," McClendon said. "He's been working hard and he's actually been swinging the bat better than the numbers indicated down there. For me, he was the logical choice. We've got a 15-day DL [with Saunders], and [Montero is] on the roster. It just makes sense to bring this young man up and give him the opportunity."
Montero was regarded as one of baseball's premier hitting prospects when acquired by Seattle from the Yankees in the Michael Pineda trade in 2012, and he batted .260 with 15 home runs and 62 RBIs in 135 games while splitting time between catcher and DH as a rookie that season.
But Montero lost his job as the starting catcher early in 2013 after hitting .208 with three homers and nine RBIs in 29 games. He was sent down to Tacoma, underwent arthroscopic knee surgery, and then was suspended for the remainder of the season in the Biogenesis case.
Hart is likely to be out at least another few weeks as he's just now starting to do some initial work in the batting cages and hasn't begun running yet on a hamstring he injured three weeks ago.
The Mariners recently signed veteran outfielder/first baseman Xavier Nady to a Minor League deal, but he's batted just .175 in his first 11 games with Tacoma.
The club activated Logan Morrison off the 15-day DL on Wednesday, but he's expected to play quite a bit of first base with Justin Smoak going on the DL with a sore left quad muscle.
Montero said he worked on conditioning as well as his first-base efforts while in Triple-A and will continue to do so, noting that he feels he's improving at the new defensive position. While he'll play mostly DH for McClendon, he was already planning early defensive work with infield coach Chris Woodward.
"It's getting better, a lot better," Montero said. "I've been doing my early work every single day. I'll bet today I'm going to do something with Woody. He's waiting for me. I'm here to learn and here to get better."