FORT MYERS, FLA. – They are the mules of spring training, and this is not offered in a derogatory manner. They pull a large quantity of weight where others might retreat.

They are the catchers who are invited to spring training in service to oversized pitching staffs. And as those pitchers start to disappear from the big-league clubhouse, so do the non-rostered catchers, often fortunate to have had more than three at-bats in exhibition games.

When these men are not in a bullpen providing the necessary partner for a pitcher's throwing session, they will be needed at the plate for full-scale infield or outfield drills.

They will be chugging from field to field across the Twins complex to undertake their inglorious tasks.

The Twins have a current 40-player big-league roster where the pitchers outnumber the rest of the positions 22-18.

One of those pitchers, Josh Winder, is currently shut down, and there are eight more nonrostered pitchers who need a catcher to do anything significant.

There are three catchers on the 40-player: Ryan Jeffers, Christian Vázquez and Jair Camargo, a very husky 24-year-old promoted after hitting 21 home runs (and striking out 119 times) in St. Paul last season.

The math never works in spring training. Extra catchers are needed, and into the breach this week, outlined against the blue late-winter skies of southwest Florida, arrive the "Four Mules":

In dramatic lore, they are known as Vet, Versatile, Slugger and Wide-Eyed, but those are only aliases.

The invitees this February are as follows:

Brian O'Keefe, 30, seventh-rounder to the Cardinals in 2014 draft, out of St. Joseph's University in Philly

The 6-1, 210-pound O'Keefe did not get signed by the Twins until the last minute before the opening of camp.

"At this point, I had no interest in going to independent ball, so I thought it might be over," O'Keefe said. "Then my agent called and said the Twins wanted to bring me in.

"It happened very fast. This is my sixth big-league spring training, always as an invitee. Work hard and hope you get in some games, get a few at-bats."

O'Keefe made it to the big leagues with the Mariners for two games at the end of the 2022 season — allowing him to partake in the celebration when the Mariners reached the playoffs for the first time in 21 years. "That was great to be around, and then last year, I got a chance to play in a few games later in the season," he said.

The M's designated him for assignment in October and four months later he was rushing to get to Fort Myers.

The preparation is a bit different these days than when pitching coach Johnny Podres was standing nearby smoking a heater, saying, "Let's see a changeup," as Twins pitchers threw a full bullpen four decades ago in Orlando.

Now, the catchers get a scouting report and a conversation with their coach, Hank Conger, before catching a full mound session.

"I had Griffin Jax today," O'Keefe said this week. "Lot of good arms here. I can see that."

Chris Williams, 27, eighth-rounder for the Twins out of Clemson in 2018

This is his second consecutive spring training as a Twins invitee. He played more first base than catcher in St. Paul, since the Saints had Camargo as a No.1 catcher. Williams hit 21 home runs and drove in 75 in 95 games.

He's rooming in Florida with Kody Funderburk, a Saints pitcher who broke through and reached the Twins last season.

"The big leagues don't seem that far away when you're in St. Paul … 10 miles, right?" Williams said. "Hope you get a few at-bats here this spring and do something with those."

Alex Isola, 25, 29th-rounder from TCU in 2019

He had a good power season at Class AA Wichita with 20 home runs, 58 RBI and a .279 average in 110 games.

"I'm hoping to be in St. Paul to start this season," Isola said. "I think I proved myself in Double-A."

Pat Winkel, 24, ninth-rounder from UConn in 2021

He has the advantage of being a lefthanded hitter, the only catcher who does so among seven in camp. He was also at Wichita, with 10 home runs, 48 RBI and a .266 average in 2023.

"I got the call about having an invite in mid-January," Winkel said. "That was exciting, knowing I was going to be around big-leaguers.

"Now, you hope to get a few at-bats and show that you can do the job behind the plate."

Those are the Four Mules for 2024. There will be other ones next February.