"He was having a great, great game," coach Bruce Arians said of Howard. "I thought Tommy (Brady) was gonna throw it to him for the touchdown when he threw it to Ke'Shawn, but it looks like he has a ruptured Achilles and will probably be done for the year."
Howard's injury happened in the fourth quarter. Howard caught three passes for 50 yards, snagging a 28-yard touchdown grab in the third quarter to pull the Bucs within three points after being down 17 in the second quarter.
"It's a tough injury," Brady said. "I think everyone feels for O.J. and what his commitment's been to the team through the offseason, training camp -- he's just been a great player for us. It sucks to lose him. It's a tough injury."
The 19th overall pick in the 2017 NFL draft, Howard's rookie season ended prematurely with an ankle injury, as it did in 2018 with foot and ankle injuries.
The Bucs are already without Pro Bowl wide receiver Chris Godwin, who suffered a hamstring injury against the Denver Broncos last week. They also were without Leonard Fournette, who suffered an ankle injury last week. They head to Chicago for a Thursday night game.
"I don't think Chris will be ready," Arians said. "Leonard has a chance. But losing O.J. will be huge."
Without Howard, the Bucs have just one true blocking tight end on their current roster: Rob Gronkowski.