Evan Gattis missed his seventh consecutive game on Monday because of illness and manager Fredi Gonzalez said doctors are trying to figure out why Gattis is taking longer than expected to recover.

Gattis began feeling ill on Sept. 7 while playing the series finale at Miami. He was diagnosed with strep throat and sat out the Braves’ series at Washington and Texas.

Gattis visited with Braves doctors when the team returned to Atlanta on Monday.

“He is trying to figure out why this thing is lingering,” Gonzalez said Monday before the series opener against Washington at Turner Field. “They are trying to figure out what is going on. He was starting to feel a little better during the weekend. Hopefully we get an answer. “

Christian Bethancourt was the starting catcher on Monday. It will be Bethancourt’s sixth game in the lineup in place of Gattis.

Gattis leads Braves regulars with a .507 slugging percentage that includes 22 home runs in 359 at-bats. He missed 17 games spanning June and July because of a bulging thoracic disk in his back.