Marrone did not want to go into specifics about the severity of the injury, but he said the team will place Lee on injured reserve later Monday and Lee will have surgery in the near future.
"Obviously it's a loss for us," Marron said. "Marqise brought a level of toughness to that room. He was obviously a very productive player for us in the past, specifically on third down. I do feel, though, once he starts recovery we want him around the team. I think he can help us."
Lee was injured during the first quarter of the Jaguars' 17-6 victory over Atlanta on Saturday night when he was tackled by Atlanta safety Damontae Kazee after catching a pass over the middle of the field. Lee's left knee buckled immediately, and he grabbed it with both hands. Kazee was penalized on the play for lowering his helmet to initiate contact, and replays showed his helmet made contact with Lee's knee.
The entire Jaguars receiving corps came out to be with Lee as he was put onto a cart and exited the field.
Kazee tweeted well wishes to Lee after the game.
Lee, who signed a four-year, $34 million contract ($16.5 million guaranteed) in March, is the Jaguars' most experienced receiver, with 171 catches for 2,166 yards and eight touchdowns in four seasons with the team. He led the Jaguars in receptions (56) and was second in yards (702) in 2017. He's also the best blocker among the receivers, so his absence will also impact the perimeter of the run game.
The Jaguars' most experienced receiver now is fifth-year veteran Donte Moncrief, who caught 152 passes for 1,875 yards and 18 touchdowns in four seasons with Indianapolis. The Jaguars also were expecting significant growth from second-year players Keelan Cole (who led the team with 748 yards receiving last season) and Dede Westbrook. Rookie DJ Chark, the team's second-round pick, will have to play a more significant role as well.
"I feel very confident about the players that we have at that position," Marrone said. "I still it as competition there. We're not settled on some of the spots at receiver, but we feel that we're good enough to go into the season with the guys that we think can make the team."