The 22-year-old Venezuelan is one of baseball's premier young hitting prospects, but the debate among scouts and baseball executives has been whether he can play behind the plate at the Major League level.
That question won't be answered in a day, or perhaps even in an upcoming rookie season in which Montero will likely catch a couple games a week for Seattle while being used primarily as a designated hitter. But Montero certainly hasn't embarrassed himself at catcher this spring.
And if you're searching for small signs, the 6-foot-3, 235-pounder provided a positive one when he threw out Reds leadoff hitter Brandon Phillips trying to steal second in the first inning of Tuesday's Cactus League game in Goodyear.
That play wasn't lost on veteran pitcher Kevin Millwood, who was on the mound with Montero that afternoon. Millwood, who has won 163 games in his Major League career, played with Montero a year ago for Scranton/Wilkes-Barre, the Yankees' Triple-A club.
"He's gotten better," said Millwood. "That's all you can ask of him. I don't think anybody is asking him to go out and be a Gold Glove catcher right away, but he's definitely improved."
Montero isn't a fast runner, but seems to be a quick study. And while he's clearly going to be forever valued more as a batter than a backstop, he's able to move his feet well enough behind the plate to be a capable catcher, and he's worked hard this spring to refine his techniques on blocking balls and getting a quicker release on his throws.
Nailing Phillips was nice feedback on the work he's done, both for him and the Mariners.
"I do that every day as a routine before a game, throwing, blocking," Montero said. "I want to do it in a game as well. I don't expect to throw everybody out, that's hard sometimes, but I got a good shot right there, put the ball on second base and he was out."
Mariners manager Eric Wedge, himself a former catcher, likes the growth he's seen this spring.
"This is a young man that is still working into the position," said Wedge. "But like I've said all along, this guy is going to be a big league catcher, and I think at some point in time, he's going to be an everyday big league catcher.
"He's working really hard with [catching coach] Jeff Datz. He's excited about the position. He understands we don't have to fast-forward this, we can take it at our pace -- and that's what we're going to do."
That means veteran Miguel Olivo will continue handling the bulk of the catching chores this season, and the club also likes John Jaso, acquired from Tampa Bay about six weeks before the Montero deal.
But Wedge wants to pencil Montero into the lineup most every day, which means a lot of DH duty and a likely fifth spot in the batting order, whether he's catching or not. The youngster has hit .306 this spring, with two home runs and a team-leading 11 RBIs in 11 Cactus League games as the Mariners head to Japan now to open their regular season with a two-game series against the A's on Wednesday and Thursday in Tokyo.
Montero's ability to hit to the opposite field with power should make for a nice fit this year in Safeco Field, which is tough on right-handed pull hitters. But he also can "turn and burn" when he wants, as Wedge likes to say, and he showed more of that in the final Cactus League games.
Montero doesn't worry about critics who think he'll never be a big league catcher, and neither do the Mariners. A year ago, word was that Dustin Ackley wasn't a good defensive second baseman, but he quickly proved that wrong after being promoted to the Majors in midseason.
Montero wants to be a catcher, which says a lot given the rigors of the position. And the Mariners will give him every chance to succeed there.
"I like being in charge of a game, calling the games, controlling the game," he said. "You're in the action a lot. That's fun."
Montero has caught all of the Mariners' starters except Jason Vargas so far this spring and says the group is impressive. Topping the list, of course, is Felix Hernandez, whose home in Venezuela is not far from Montero's upbringing in Guacara.
The two hadn't met before Montero was traded to Seattle, but it didn't take the youngster long to learn who was King.
"Nobody touches his pitches," Montero said with a grin. "That's different."
Montero was fairly quiet early in Mariners camp, but seems to be fitting in more and more as time passes. He admits it was a shock being traded for the first time after spending five years in the Yankees organization and then hitting .328 with four home runs and 12 RBIs in 18 games as a September callup last season.
"I like being here," Montero said. "Everybody is fun and these are good people. I hope this year will be different and we'll win more games and do better for Seattle."
Much of that will depend on whether Montero and the rest of a youthful offensive core built around Ackley, Justin Smoak and Mike Carp can produce better numbers for a team that's finished last in the American League in scoring three straight seasons.
If they do, if Montero helps lead that turnaround and continues developing behind the plate as well, then the Mariners will have made quite a catch, no matter how Pineda develops for the Yankees.