CINCINNATI -- Buffalo Bills tight end Charles Clay, the team's leading receiver, was carted to the locker room after suffering a knee injury in the first quarter of Sunday's 20-16 loss to the Bengals.

Clay was hit in his left leg by Bengals safety Shawn Williams after a 24-yard catch. He remained on the ground in apparent pain before being walked to a medical tent on the sideline with assistance from two members of the Bills' training staff. Clay later walked gingerly to an awaiting cart.

He was expected to be Bills quarterback Tyrod Taylor's top target Sunday because top wide receiver Jordan Matthews was out with a thumb injury. Clay caught five passes for 112 yards in last Sunday's win over the Atlanta Falcons, and his 227 receiving yards led the team entering Week 5.

Bills tight end Charles Clay was carted off with a knee injury Sunday. AP Photo/Gary Landers

In place of Clay, the Bills' top tight ends are Nick O'Leary and Logan Thomas, a former quarterback whom the Bills signed last season as a tight end.

The Bills also ruled out cornerback Leonard Johnson with a hamstring injury.