FORT MYERS, Fla. — Ruben Amaro Jr. is still in baseball. But probably no one is making such a strange position shift this spring.

Fired as Philadelphia’s general manager last September, the former big leaguer now arrives at Red Sox camp in the early morning and prepares to return to the field as Boston’s first-base coach.

“Pretty dramatically different,” Amaro said Sunday. “Just physically, I had to get myself in much better physical condition. I started that almost immediately after the season when I found out I was going to be joining the organization in this capacity,” he said.

“Changed my diet a little bit, worked out a little bit, made sure I got some fungos in and threw some BP in the offseason, because it had been a long time since I did any baseball-related activity,” he said.

Amaro, 51, was hired by the Red Sox during the offseason after being fired by the Phillies last September, following seven seasons as general manager. Before that, he spent 10 years as an assistant GM.

After years of suits and ties, phone calls and contracts, Amaro has gone back to wearing jerseys and caps, and picking up a bat and a glove again.

It started with a phone call from Red Sox Manager John Farrell, his former teammate in Cleveland.

Amaro played eight seasons in the big leagues, mostly as an outfielder, batting .235 with 100 RBI and reaching the World Series with the Indians in 1995.

“To me it’s about getting a brand new opportunity,” Amaro said. “For me it’s about baseball, it’s the game. That’s all I’ve ever known.”

He played for three organizations and, except for a few charity events, hadn’t really picked up a bat or glove since retiring in 1998.

It’s a big change from going into the office or just observing the on-field action.

He said he usually arrives at the park around 5:30 a.m. and gets in a workout before meetings start around 7.

“Probably the most difficult thing is getting these guys to know me,” he said. “They didn’t know me from Adam – except for the fact that I may have tried to trade for all of them.”

His biggest test so far has been throwing batting practice. He’s ambidextrous, and one of his arms hasn’t come back quite as strong.

“That’s still a work in progress,” he said, smiling. “Right now my right arm is a little balky.”

He knew he needed the support of his family to make such a career change.

“Now there’s a real schedule I don’t get to make myself,” he said. “They were understanding about this path.”

Amaro said that one day he might like a chance to manage – like former Miami GM Dan Jennings, who went back into the dugout last year – or may want to return to the front office.

But, for now, he’s adding to his baseball resume.

“I’m just trying to leave all my options open,” he said.

“This is a great opportunity for me to be on the dirt to rub elbows with the players, be closer and see what it’s like to be on the field again. It gives me perspective whether I’m on the field or I’m back in the front office.”

NOTES: Farrell said left-hander Eduardo Rodriguez underwent an MRI Sunday morning after injuring his right knee during workouts Saturday. “He suffered a subluxation of the patella (tendon). As far as structural damage, there isn’t any,” Farrell said, before explaining that Rodriguez will undergo treatment for swelling and they’ll know in 72 hours if the damage is more severe. …

The Red Sox open exhibition play Monday with their annual doubleheader against Boston College and Northeastern.