The Cincinnati Bengals tight end left the Pro Bowl in a walking boot, but downplayed any long-term effects, saying at the time, "I'll be good."
Months later the ankle still hasn't responded positively.
NFL Media Insider Ian Rapoport reported Eifert will undergo ankle surgery and likely will begin training camp on the physically unable to perform list.
The Cincinnati Enquirer reported it will be a "minimal procedure" on Eifert's ankle. The recovery period is estimated at three months, per the Enquirer, which could put Eifert's availability for the start of the season at risk.
Rapoport later reported that Eifert, who is undergoing the procedure Wednesday, could miss the first few games of the season in a worst-case scenario.
Eifert, 25, has dealt with injury problems throughout his career, including missing 15 games in 2014. The tight end missed three games last year.
The 6-foot-6 tight end proved last season that when healthy he can be a touchdown machine, hauling in 13 scores. The Bengals picked up the fifth-year option for the former first-round pick earlier this offseason.