Eifert suffered a broken ankle and was carted off the field in the third quarter Sunday at Mercedes-Benz Stadium in Atlanta. He had four catches for 38 yards and a touchdown before departing.
Sources told NFL Network that Eifert's broken ankle will cost him the season, with surgery "imminent."
The score was Eifert's first since December 2016. The 2015 Pro Bowl selection had 15 catches for 179 yards and a score in four games this season. He has played a total of 14 games in the last three seasons combined following his Pro Bowl campaign. Eifert pulled in 52 catches for 615 yards and 13 touchdowns in 13 games during the 2015 season. He hasn't appeared in more than 13 games in a season since his rookie campaign in 2013.
"This was the hardest I've worked to put myself in a position to help this team succeed and having this happen crushes me," Eifert tweeted Sunday night.
"If I've learned anything from before, it's not a time for self-pity and negativity. The only thing to do is move forward with optimism, With the support of my family, friends, trainers, teammates and coaches, this will soon be another obstacle that was overcome and life will go on. Thanks to everyone who has sent prayers and well wishes my way."
San Francisco 49ers tight end George Kittle offered his support by responding to the tweet, writing "bounce back man."
"Bro, I already know you got the heart of a lion," Tate wrote on Twitter. "Never ever will doubt that. We know you coming back better and stronger."
Falcons linebacker De'Vondre Campbell landed on Eifert's lower right leg, causing the injury. Campbell said he is praying for Eifert.
"I never take the field with thoughts of intentionally hurting anyone, I just try to do my job to the best of my ability," Campbell tweeted. "Praying for a speedy recovery Tyler Eifert. I appreciate the opportunity to compete against you."
"We were still talking. Andy [Dalton] said, 'C'mon guys we've got to win it for him. We've got to continue to march it and continue to keep fighting.' It's a whole bunch of leaders in our offensive group," Bengals wide receiver Tyler Boyd told reporters Sunday. "We don't wait for one guy to say it. We all know, we all stick among each other, and we get the job done."