An MRI taken on Jordan Schafer’s right ankle Friday revealed a stress fracture, known as an intraosseous fracture, Braves general manager Frank Wren said Friday night.

It’s a rare fracture to the inside of the bone and did not show up on either of two X-rays taken in recent weeks.

“If we had (taken an) MRI at the time of the injury, this fracture would not have shown up,” Wren said. “It’s the type thing that over time, you get a better sense of it. It’s one of those strange situations.”

Wren said the injuries typically require six weeks to heal. Schafer is already 2 1/2 weeks into that process.

“It’s on its way to healing,” Wren said. “It’s probably a six-week injury, and so he’s a couple weeks into that now. Nothing really changes. It’s going to take time.”

Schafer first fouled a ball off his right ankle in Kansas City on June 26, and initial X-rays were negative. He rested for a week and attempted to come back in a couple of pinch-hit at-bats July 2 and 3. X-rays were taken again when pain persisted, and he was placed on the disabled list July 4.

Schafer was back on the field taking batting practice Wednesday in Miami, but continued to feel pain running. Wren said doctors didn’t believe playing on it for those two at-bats exacerbated the injury.

The Braves were already short-handed in the outfield given Schafer’s injury. Then they watched both Jason Heyward (hamstring strain) and B.J. Upton (adductor strain) leave the first two games of the series against the Reds. The Braves had hoped to get through the weekend to the All-Star break without having to make a roster move, but that could change now.

“That may have changed,” Wren said. “I think we’ll talk after the game and see where we are, once we get a better sense of everything.”

J-Hey update: Heyward said his strained right hamstring felt better Friday, a good indication that he avoided the worst when he injured it running the bases Thursday night. Heyward is considered day-to-day, but the Braves plan to rest him through the weekend series against the Reds, giving him a full week's rest when play resumes after the All-Star break.

“If we could just keep improving every single day and just get him through the weekend, I think we’ll be in good shape when we come out from the All-Star break,” Braves manager Fredi Gonzalez said.

Reed Johnson took Heyward’s spot in right field Friday night and is expected to play throughout the weekend. Gonzalez said if need be, he could use Tyler Pastornicky or recent call-up Joey Terdoslavich in the outfield.

Heyward felt his hamstring grab in the second inning Thursday night, a step or two shy of third base after advancing from first base on a Justin Upton single. He spent Friday afternoon alternating between ice and treatment on his hamstring.

“I feel better today than I did last night,” Heyward said Friday afternoon. “More flexibility in my hamstring, less pain, not as uncomfortable, but there still is pain. It’s still really sore.”

Heyward didn’t completely want to rule out playing this series, but realizes it’s probably the smarter choice.

“If I feel great tomorrow then we’ll see about (Sunday), but right now the best thing to do is be cautious, knowing that there are four days coming up off with the All-Star break,” Heyward said. “It would be good to get this time to rest and come back and not worry about further hurting myself (by) coming back too soon.”

Heyward was heating up at the plate, hitting .290 (42-for-145) with five home runs, 13 RBIs and 15 multihit games in his past 36 games since June 3. He hit .153 (17-for-111) with three home runs and 10 RBIs in his first 32 games, before and after the month he missed after an emergency appendectomy.

J. Upton's adjustment: Justin Upton is experimenting with a change in his mechanics and seeing immediate results, virtually eliminating his leg kick as he starts his swing.

Braves hitting coach Greg Walker said he and Upton talked about simplifying his “load” for a while, but that Upton decided to take it into a game in Miami and liked what he felt.

“It just keeps him more consistent to the launch position,” Walker said. “Everything gets there easier, earlier, quieter. It’s more efficient.”

Upton was 5-for-10 in the first two games of that series against the Marlins, with four doubles, a home run and five RBIs. He broke through with a two-run double in the 14th inning of the Braves’ 7-1 win Monday night.

He left Friday’s game with a left calf strain, which ocurred as he ran out a ground ball in the seventh inning. He’ll be re-evaluated Saturday.

After hitting .217 in May and June combined, with five doubles, one triple, three home runs and 18 RBIs, Upton was 3-for-4 against the Reds on Thursday night to raise his July average to .319 (14-for-44). He has six doubles, one triple, one home run and eight RBIs in 10 games this month.

Walker called this the early stages of the adjustment. He said Upton’s initial apprehensions came because he thought it might cost him power.

“I think his fear all along is he’s going to lose some pop,” Walker said. “But he’s got so much pop that we felt like all along he could give up some of that for more efficiency.”

Upton led the major leagues with 12 home runs in April. He’s had four since, but he could take some confidence from the home run he hit Tuesday night in Miami.

“I’m taking my base hits,” Upton said. “I ran into the one the other night — the ball left the yard for me — so you’ve got to be patient. I’m being patient with myself right now.”