LAKE BUENA VISTA, Fla. – When Melvin Upton Jr. went to the doctor Friday about his sore left foot, the Braves center fielder figured he’d be told to rest a few days.

“Ten minutes into it I had a cast on my foot,” said Upton, who’s expected to miss all of spring training after being diagnosed with sesamoiditis, or inflammation in a bone behind the ball of his foot. “I went into it thinking a week at the most. I thought after a couple of days it would be fine.

“The doctor saw some things that they didn’t like, and here I am.”

He was on crutches Saturday when he met with reporters at his locker at Champion Stadium, with a sock covering a cast that covered his left leg from the foot to just below the knee. Upton will likely wear the cast for two weeks, then a protective walking boot for another four to six weeks.

The Braves say they plan to go with in-house options in center rather than pursue another replacement. They already had a few players who were going to get significant playing time this spring, so they would have a pecking order or replacement in the event that Upton struggled as he has in each of his first two seasons with the Braves.

Now, those players will be competing instead for a spot in the opening-day lineup.

The four candidates including offseason acquisitions Eury Perez, Eric Young Jr. and Zoilo Almonte, and returning Braves minor leaguer Todd Cunningham. Almonte is the only one without plenty of center-field experience, having played corner outfield positions in the Yankees organization.

“I’m sure there’s guys that are pretty excited, some of the guys in that locker room,” Braves manager Fredi Gonzalez said. “I really would’ve liked to see if all the hard work B.J. was doing this winter would’ve paid off. Now we’ve got to wait a little bit. I don’t think it’s going to hurt him, just have to wait a little bit longer.”

Upton will be able to lift weights and do other upper-body work, but probably won’t be cleared to resume baseball activities until early April. The Braves play their regular-season opener April 6 at Miami and might not have Upton on their major league roster until at least a month later.

“Yeah, it’s frustrating,” Upton said. “But at the same time I’m going to try to take the positive out of it, and at least it’s now and not in August in the middle of a pennant race. If it’s something that we can get ahold of now and knock it out, it’s something that we can hopefully never have to deal with again.”

Coming off back-to-back seasons that were the worst of his career, Upton must wait longer to see if offseason work he did on his swing — alone and with hitting coach Kevin Seitzer — will pay off. He and Seitzer had planned to continue that work during spring training, but now those plans are on hold.

Upton hit just .198 with a .279 OBP, 21 homers and 324 strikeouts in 1,028 plate appearances in his first two seasons of a five-year, $75.25 million contract, and the Braves tried this winter to trade him but could find no team willing to take on any significant part of the more than $46 million he’s still owed.

When he reported to camp this week, he announced he would go by his birth name, Melvin Upton Jr., rather than B.J. Upton, which he’s used previously throughout his pro career.

He said the foot ailment cropped up this week and wasn’t the result of any specific swing or other activity as far as he could tell.

“No, it was kind of a gradual thing,” he said. “I let the trainers know ahead of time that there was something there, but I didn’t think anything of it. Just went out and did my thing, and before the end of the first (full-squad) workout (Thursday) I couldn’t really walk on it. Came in the next day and it wasn’t bad, but it definitely wasn’t good.

“Like I said, I thought it’d be a week at the most. It turned into a little bit longer than that.”