Eifert was placed on injured reserve with a designation to return after suffering an elbow injury in a season-opening victory over the Baltimore Ravens. The designation made him eligible to play against the Cleveland Browns against Nov. 6.
Lewis said Friday that Eifert underwent surgery a couple of weeks ago for a shoulder injury he sustained in training camp. The Bengals coach reportedly added that he expects Eifert to be ready for next season.
"It's been unfortunate for him, but this was the best way for him," Lewis said, according to Cincinnati.com. "The elbow took longer. Because you have the shoulder (problem) and the (lingering) elbow (problem) the strength to play NFL football was moving away fast."
Eifert, 24, is in his second season in the league after being selected in the first round of the 2013 draft out of Notre Dame. Last season he caught 39 passes for 445 yards and two touchdowns.
The Bengals (10-4) face the Steelers in Pittsburgh on Sunday.