A source told ESPN's Adam Schefter that the Jaguars fear the ACL is torn.
Coach Doug Marrone will have additional updates during a Monday afternoon conference call, according to the team.
Robinson was hurt on the third play of Sunday's game, after he caught a 17-yard pass from Blake Bortles on third-and-2 to convert the first down. He was unable to walk to the sideline and was immediately attended to by the Jaguars' medical staff.
Robinson eventually walked off the field and was taken to the locker room to undergo further tests. He did not return.
Robinson is entering the final year of his rookie contract, and the sides have had preliminary extension discussions.
Robinson, who has 202 catches for 2,848 yards and 22 touchdowns in his three-plus seasons, is the Jaguars' best receiver. His absence means the team will have to rely heavily on Marqise Lee and Allen Hurns, as well as veteran Arrelious Benn, who is one of the team's core special-teams players. Additionally, undrafted rookie Keelan Cole likely will be more involved.