To the untrained eye, the swings looked crisp, tight and absolutely right. But not to Mattingly, who assembled the group behind the plate and broke down each swing with unfettered accuracy.
Lesson learned, Mattingly clapped his hands together and stretched out his arms as if to say, "See?" And as Jason Giambi, Hideki Matsui, Doug Mientkiewicz and Alex Rodriguez nodded and scattered, another Mattingly mini-clinic was complete.
Mattingly may have been promoted to become Joe Torre's bench coach this season, ceding his duties as hitting coach to Kevin Long, but he can't resist the urge to chip in with a few pointers for his love of hitting.
"You've got to be ready to help these guys out," Mattingly said. "You've got to be here for them -- not for yourself. I'm here for their success, not my success."
It is that passion that leads at least one Yankee to believe that, when Torre's highly successful run as the team's manager comes to an end, Mattingly will be the one assuming the dugout reins.
"He'll be perfect. He'll definitely be, in the next couple of years, the manager of the Yankees," Giambi said.
"He's got a great name to play in New York, he knows how to handle the press and he knows a lot about the game. I think that's one of the main reasons he went to bench coach."
Taking the helm of a Major League club is a thought that prompts Mattingly to grin slightly, if not awkwardly.
As he spoke of the possibility of someday managing the Yankees, his mentor, Torre, sat about 15 feet away in the manager's office, kicking back in a reclining chair as he dutifully completed paperwork.
Mattingly is not looking to push Torre, who is in the final year under contract with the Yankees, out the door. But Mattingly also can not ignore those, like Giambi, who have touted him as Torre's likely successor.
"I don't worry about it, to be honest with you," Mattingly said. "I don't worry about the future. I'm 45 years old, and it's not like you're a player and the clock is running on your skills.
For Torre, Mattingly's work ethic became evident during seven seasons as a guest instructor at Yankees Spring Training from 1997-2003, long before he ever tinkered as the team's official hitting coach.
One of the most popular players in the franchise's history, it would have been easy for Mattingly's spring excursion to have taken on little more meaning than showing up in Tampa, putting on a No. 23 jersey and waving to fans.
Mattingly wouldn't dream of it, annually exhibiting the same workmanlike nature that led him to stroke 2,153 hits in the Major Leagues.
"It wasn't just a vacation for him," Torre said. "He didn't just come down to hang out. He wanted to do some good. I told him to let me know if he was ever thinking about doing something full time, because he definitely had the capabilities."
Mattingly finally made that call for the 2004 season, with the blessing of his wife, Kim, and their three sons -- Jordon, Taylor and Preston.
After his retirement following the 1995 season, Mattingly said he spent most of his time back in Evansville, Ind., "chasing kids around Pony League fields," tending to horses and tweaking the designs of what would eventually become his budding Mattingly Baseball bat company.
"I didn't want to be in New York until I was 39, and the kids would be out of high school and not even know who their dad is," Mattingly said. "I was able to do that, and as the kids grew up, they were kind of like, 'Go ahead, Dad.' It made it easier for me to make the transition."
The Yankees have not even played their first exhibition of 2007 yet, and already Torre has acknowledged Mattingly's dedication and efficiency.
Each day at Legends Field, Mattingly arrives early and leaves late, digging through statistical data and scouting reports looking for something -- anything -- that could give the Yankees an edge during the regular season.
"I do look at a lot more stuff," Mattingly said. "When I was the hitting coach, all I did was study the opposing team's hitters. That was the sliver of the game I was responsible for.
"Now, I'm here to help any way I can and assist Joe. I can be another set of eyes for him. There's so many decisions to make in the course of a game, and I want to make it easier for him. The information will be at his fingertips. We'll be prepared."
The Yankees would expect nothing less.
Bryan Hoch is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.