Don Mattingly uses some Jim Leyland wisdom.

KEY BISCAYNE — How best to spend spring training eve? For the Marlins’ coaching staff and baseballoperations personnel, the answer was to get to work. They decided to huddle Monday night to review their pitchers and catchers, who report to Jupiter on Tuesday for physicals in the morning and a workout in the afternoon.

That’s when the real work will start, though manager Don Mattingly began shaping the specific mindset he wants his players to adopt by sending them all a letter last month.

The letter, made public last week by Hall of Fame baseball writer Peter Gammons, is addressed to “All Major League Spring Training Attendees” with the subject line “Little Things Matter A Lot.”

In it, Mattingly goes on and on about the proverbial Little Things, “a common phrase in our business that is used so often, yet so casually forgotten in the course of a long season.”

The walk before a home run, the slide that breaks up a potential double play, owning up your mistakes — it’s not always pretty or noteworthy, but it all makes a difference.

“There is no doubt in my mind that we are a team about to emerge as a contender,” the letter reads. “I sincerely believe if we have a deaf ear for those trying to destroy us and a receptive ear for those trying to help us, we will achieve. I have no reservations that if we do the Little Things we will be rewarded.”

Then came the grand reveal: It isn’t Mattingly’s letter. Jim Leyland, the former Marlins manager, wrote it and sent it to his Pittsburgh Pirates team in 1988.

Mattingly came upon it, though he said he doesn’t remember how, and he couldn’t help but pass it along to his guys.

“I didn’t tell Jim I did this. I hope he didn’t care,” Mattingly said Monday at the Jack McKeon Celebrity Golf Classic at Crandon Golf. “It fit our club perfectly. … This letter was written 29 years ago. It’s all the same stuff that we talk about almost every year.”

Bour’s on first

Justin Bour is the Marlins’ everyday first baseman.

“We think there’s a lot in the tank with this guy,” Mattingly said Monday. “He brings fear to the lineup.”

Mattingly pointed out that Bour was having a fine 2016 until an ankle injury in July derailed his season. At the time of the injury, Bour had a .268/.347/.526 slash line to go along with 15 homers and 46 RBI in 68 games.

The big change for Bour will be facing left-handers regularly. In only 110 career plate appearances against southpaws, he has hit .223 with a .273 OBP and .291 slugging percentage.

The Marlins, who will be going with a short bench to carry an extra reliever, crave versatility with their position players. That’s true of

Miguel Rojas and Derek Dietrich, who will both back up Bour in addition to playing other positions, as well as catcher J.T. Realmuto, who will try learning first base in camp.

If Bour can produce the way the Marlins hope, it won’t matter much who backs him up.

“This is a guy who has an opportunity,” Mattingly said. “We think he’s getting better.”

AP/FILE Miami manager Don Mattingly says he didn’t ask permission from Jim Leyland before reusing one of his letters.