Coming from baseball's youngest batting champion, it was high praise. Two months later, as Garcia prepares with the rest of the Tigers for the World Series, and looks to add more entries to his spot in Tigers postseason history, it's looking like one of the best August moves in baseball this year.
Detroit, meanwhile, believes it's a sneak preview of what's to come.
"There's no question he should be a really good player," Kaline said. "You know he's still got some holes in him, but he's a baseball player. And he should be a good player, really good."
That's not to say that Castellanos won't be. And the main point of Kaline's rare trip to the Double-A club was to help him along the way. But when the Tigers needed a late-season callup to fill the right-handed-hitting outfielder role, they weren't looking down the road.
"We had some injuries and problems going on with Ryan Raburn, one of our good right-handed hitters, that had hit some home runs, and we thought would be very productive this year, and that wasn't happening," manager Jim Leyland said. "And we needed a right-handed hitter."
Kaline went to Erie about a month after Castellanos moved from third base to right field to give him a chance to crack the big leagues sooner. In Detroit, the list of great right fielders begins with Kaline, who manned the position for two decades at Tiger Stadium.
Kaline is Mr. Tiger for a reason, not just for his greatness over 22 seasons in the field, but for three decades of contributions since he hung up his spikes. He has spent more than a decade as a special assistant. Even at 77, he spends Spring Training working with Tigers outfielders on defense.
That was the goal of his visit, primarily with Castellanos, but also with Garcia and Daniel Fields. With Castellanos, he had a model student, loaded with questions and eager for feedback. It was perfect for Kaline, who's willing to give out as much information as a player wants.
Garcia had played right field before moving to center when the Tigers shifted Castellanos.
"We worked with them for three days in a row, [outfield instructor] Gene Roof and I," Kaline said. "And you could see that Garcia was really an accomplished outfielder. You could see it, even though he was playing center field down there. We knew he could play right field, and had played right field [at Class A Lakeland].
"And Nick was learning. He tried and everything. He's a great kid and he's going to be a really good player, but he wasn't ready to play the outfield yet. And you can't expect [that from] a kid who's been an infielder his whole life."
In Garcia, Kaline saw a cannon arm and good instincts. He saw speed he didn't recall seeing in Spring Training, maybe because he wasn't in center. In three days, he saw an outfielder who could make an impact now. He didn't sit among the top prospects, but his combination of speed, quick bat and power made him a sleeping giant of a prospect at 6-foot-4 and 240 pounds.
Just to be sure, Kaline checked around.
"In talking with the coaches and talking to the other managers on other teams, they said that Garcia right now is the better player," Kaline said. "So when I came back, I made the recommendation. I talked to [team president/general manager] Dave [Dombrowski] and I said, 'Hey, Garcia can really play. I don't know what he can hit up here, but he can play the outfield.'"
It wasn't the only opinion Dombrowski gathered. One of Dombrowski's strengths, according to many in the industry as well as Tigers officials, is his ability to gather evaluators he trusts and listen to them.
The feedback, Dombrowski said, "came in from everywhere, really, at that point. It came primarily from player development, and that would be one where I lean on [assistant general manager] Al [Avila] a great deal."
Still, Kaline's opinion carries weight in the organization. Moreover, many player development officials agreed with him. What they couldn't predict was how a 21-year-old with less than four full years in the country could handle not only the big leagues, but also a playoff race.
They've been aggressive in that situation before. Five years ago, they called up 20-year-old Cameron Maybin, a similarly great athlete, and soon realized they had rushed him. That didn't cost the Tigers the division to the Indians, but it didn't help either.
Still, they needed somebody. He was their best shot.
"They thought this kid could handle it," Leyland said.
Not only did they call Garcia up, they did it on Aug. 31, ensuring he'd be eligible for the postseason. Nobody expected he'd play this big of a role, however.
"I think sometimes, when you have young players, it's just like a trade: sometimes they rise to the occasion, and sometimes they get overwhelmed," Dombrowski said. "One thing is, it doesn't look like he's been overwhelmed at all."
Garcia has earned comparisons to Miguel Cabrera for physical resemblance, his ability to hit to the opposite field, and his forecast to eventually hit for power. What they've seen is an ability to flick pitches out to right field like another Venezuelan great, former Tiger Magglio Ordonez.
Kaline loves that.
"Most young players want to hit it out of the stadiums," he said. "And I don't care who you are, when you try to do that, you're not going to do it. You're going to make a lot of mistakes hitting-wise. He's been actually mostly hitting the ball to right field, which makes you stay on the ball a little more. He's putting the ball in play and getting base hits to right field and even up the middle."
Garcia went 15-for-47 (.319) in September, including 10-for-30 off left-handed pitchers. Those hits were all singles, but they were frequently productive.
After going 1-for-7 in the American League Division Series, Garcia went into the AL Championship Series against a Yankees rotation with two of baseball's best lefties in CC Sabathia and Andy Pettitte. Garcia went 5-for-11 with three RBIs, including key pinch-hit singles.
He's the second Tiger 21 or younger to get a base hit in the postseason. The other was Ty Cobb.
If the Tigers face a left-hander in the World Series, Garcia will be in there -- either starting in right field against a lefty starter, or pinch-hitting against a reliever.
"I think he has done a good job," Leyland said. "He's a little overmatched at times, and probably not ready for this, but he has done well."
That might be true. The way he has looked so far, nobody thinks he's far off.
"He has this look about him," Kaline said. "He's a good guy. I think this has really been a great experience for him."
As Dombrowski said, "He is going to be a tremendous player."