When Pablo Sandoval went home to Venezuela for Christmas in 2011, he gained so much weight so quickly — 21 pounds in 21 days — that when he returned to work out in Phoenix, his personal trainer did everything possible to keep the third baseman out of sight from his team, the San Francisco Giants.

Ethan Banning, the owner of Triple Threat Performance, oversaw two successful and intense pound-shedding winters for Sandoval, ahead of the third baseman’s only two All-Star seasons in 2011 and 2012.

Banning told the Herald that he knew the Giants and Sandoval were in contract negotiations at the time Sandoval returned from the holiday looking like Santa.

The worry was that if the Giants caught a glimpse of Sandoval — they were monitoring the progress — his payday could have been in jeopardy.

“I would go pick him up at a random location, drive him to the facility so that his car wouldn’t be there, so if they dropped in they wouldn’t know he was there,” Banning said. “So for about a three-week period, he had the flu — we had every excuse in the world. We were just trying to rip weight off him again. And it ballooned way out of control.”

Banning said he sacrificed the rest of his own existence at the time to get Sandoval to burn all the fat he had so quickly added. It worked: a three-year contract worth about $17 million materialized in January 2012.

“I was coming in seven days a week, he was training three times a day on six days, and on Sundays he was training twice,” Banning said. “It was that bad. I mean, it got out of control.”

The value of that first contract for Sandoval coincidentally lines up with how much money the Red Sox are paying him this season for what amounts to nothing.

After he was placed on the disabled list with a left shoulder injury Wednesday, Sandoval went for an MRI yesterday and the results are to come in today, president of baseball operations Dave Dombrowski said. Yahoo Sports reported Sandoval told the Red Sox he wants to play or be traded, which isn’t surprising.

But even if Sandoval moves on from the Sox or loses a ton of weight, the 29-year-old’s problem won’t disappear without someone to watch him constantly, Banning believes.

The Sandoval that Banning knew is one who needs more help than he has right now, and somebody who needs to admit he has a problem.

“I care about him greatly,” said Banning, who lost touch with Sandoval after the 2011-12 offseason. “But it’s a tough love. He needs to be smart enough to say there’s a problem. It’s like the alcoholic that won’t admit he’s an alcoholic: well, you can’t address that you’re an alcoholic if you don’t ever admit there’s a problem. He’s got to address that.

“He’s proven to me and shown consistently that he’s got to have somebody like me holding his hand doing that. And it’s not an exercise thing, it’s an eating thing. Obviously exercise is an important factor in it, a very important factor, but eating is going to be the component that needs to be managed and monitored. We had a chef on staff that cooked all his meals.”

Banning said he controlled what Sandoval drank, too, which meant minimal booze.

Efforts to reach Sandoval’s agent were unsuccessful.

Banning said Sandoval is very competitive and truly a hard worker who could slim down again because he’s done it before, but it would take time.

Sandoval is also a fun-loving guy who doesn’t want to tell anyone no — “almost childlike,” Banning said.

“Twenty-one pounds in 21 days, that sounds unreal,” Banning said. “He loves to be loved by people. And he connects with people, and the way that (Venezuelan) culture connects is through food. Food is love to them.

“I flew down to Venezuela with him,” Banning continued. “When I’m there, I could say no to people and I could shake my head and people would walk away. We were there for five days, he lost a pound a day.”

Sandoval and Banning lost their relationship around the same time Sandoval got his first contract. Sandoval walked in one day to train at an unscheduled time when Banning was with a high-profile client, Banning said, and Banning told Sandoval he couldn’t do that.

Shortly after, Sandoval started training with the Giants again, and by this time, spring training was starting.

“I probably wasn’t the most gentle when I said that, because I’m not the most gentle guy anyway,” Banning said. “I don’t believe you mold steel with a feather.”

Banning also believes the contract Sandoval signed in 2012 created some ego, a resistance to be doing told what to do. It follows, Banning said, that a $95 million Sandoval could have the same attitude in Boston.

“You need the babysitter,” said Banning, who said he has not spoken to the Sox. “Hey, that’s a pretty harsh statement. At the end of the day, I’m speaking truth. … I love the guy.”

Banning took a phone call this offseason from Sandoval’s brother, Michael, whom Banning said was hoping the two would connect again.

“I think that he’s embarrassed right now,” Banning said. “I think there’s going to come this moment that he’s going to show everybody that this is not who he is. … I don’t know that it’s going to be with me, but he’s going to hire somebody like that. I think he’s likely going to figure it out. But it’s not going to be this season, and likely not with the Red Sox, the way it looks.”