ATLANTA -- Brian McCann returned to SunTrust Park on Wednesday afternoon, feeling better than he had expected. But the Braves catcher will miss the rest of this month, and possibly a portion of September, with a sprained left knee.  

The Braves placed McCann on the 10-day injured list and recalled Alex Jackson from Triple-A Gwinnett. Jackson will spend the next couple weeks sharing the catching duties with Tyler Flowers.

“[McCann] will probably need the whole IL time to just make sure [the knee] solidifies and the swelling goes down,” manager Brian Snitker said. “There’s not really a timetable, but it’s encouraging to see him walking around [in the clubhouse]. He seems to be a little more encouraged than what he thought he might be today.”

Tests showed a sprained medial collateral ligament created the left knee discomfort that forced McCann to exit Tuesday’s 5-1 win over the Marlins before the start of the fourth inning. The 35-year-old catcher missed two months last year while recovering from arthroscopic surgery on his right knee.

McCann’s only previous significant physical ailment this year was a strained right hamstring that sidelined him for 10 days in April.

A short break could prove beneficial for McCann, who has hit .212 with a .586 OPS over his past 16 games. The seven-time All-Star produced a .884 OPS through June 17. But he has hit just .222 with a .625 OPS over the 36 games that have followed.

Flowers has also struggled with the bat, and the MLB-high 13 passed balls that have been charged to him this year have only heightened the defensive concerns that the Braves have with him behind the plate.

Jackson has steadily improved since he moved back to a catching role before the start of the 2017 season. The former first round pick, who began his professional career as an outfielder, has hit .224 with 25 home runs and a .821 OPS in 328 plate appearances for Gwinnett this year. He went 0-for-10 with a walk and three strikeouts when he got his first call to the Majors when McCann was injured in April.

While the power numbers have been strong, Jackson hit .188 (16-for-85) and produced a 48.2 percent strikeout rate over his past 23 games for Gwinnett.

“He’s been struggling offensively, but in terms of the catching and throwing, the reports on that have been good,” Snitker said. “That’s what we need him to do, just come in here and catch.”

Injury updates

Dansby Swanson will begin his Minor League rehab assignment with Class A Rome on Thursday and Austin Riley will do the same Friday. Both players will serve as the designated hitter in their first game and then begin building their endurance back by playing portions of games in the field over the days that follow.

Right-handed reliever Darren O’Day is scheduled to throw an inning for the Rookie League GCL Braves on Saturday. O’Day has been sidelined since he strained his right forearm during his March 1 Grapefruit League season debut. There is a chance that the former All-Star reliever could be used out of Atlanta’s bullpen in September.