X-rays were negative for Gattis, who experienced similar discomfort in 2012 when he strained a tendon while playing for Double-A Mississippi. He missed just a couple of days after receiving a plasma rich platelet injection.
"It just came out of nowhere, so we took the day and we'll see where I'm at tomorrow," Gattis said. "We'll just go from there."
The Braves elected to pull Simmons from Tuesday night's game following the bottom of the seventh. The ankle has bothered Simmons off and on for the past couple of weeks, and he may have tweaked it during the top half of the inning.
"I feel OK, hopefully it goes away quick and the inflammation or swelling goes down," Simmons said. "Hopefully, I'll be ready to go tomorrow. ... It's not a terrible pain, it's just a nagging thing."
Grady Sizemore plated the go-ahead run Tuesday night by hitting a broken-bat comebacker to the mound. The bat distracted reliever Luis Avilan, who failed to field the ball cleanly. The ball hit Avilan's glove, causing it to change direction.
A charging Simmons was forced to cut right quickly as he barehanded the ball and threw to first to get the out.
"He moves around pretty good. He's pretty active out there," Braves manager Fredi Gonzalez said. "Sometimes, he'll aggravate it and it swells up on him, but hopefully we caught it early enough. I didn't want him to have the rest of the game to hurt it, so I took him out of the game to get some treatment, and we'll check him again tomorrow."
Simmons added: "I just felt it today. It just started nagging me during the inning. It didn't want to go away when we got done with the inning. I tried playing on, but it just didn't feel like I was going to help my team."
Mark Bowman is a reporter for MLB.com. Joe Morgan is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.