DETROIT (AP) -- Eric Ebron was on his back, looking as if he feared he was seriously injured.
The Detroit Lions tight end pounded the turf with his right fist as the team's medical personnel evaluated his lower right leg.
Ebron was later carted off the field, bowing his head and appearing distraught Saturday.
He was hurt while blocking on a play on what the team called a mock game, which suddenly became too real for a team already faced with the reality of a passing game without Calvin Johnson for the first time in a decade.
After Ebron was injured, the Lions shifted the practice that simulated game situations to the other end of the field.
"Injuries happen in football," Lions general manager Bob Quinn said.
Ebron, drafted by Detroit No. 10 overall in 2014, seemed to be a favorite target of Matthew Stafford earlier in the practice that was open to the public at Ford Field.
Stafford acknowledged being concerned about Ebron's injury.
"I have no idea what's wrong with him," he said.
Ebron started 15 games over the first two years of his career, making 72 receptions for 785 yards and six touchdowns.
Detroit's depth at tight end was thin even before its best player at the position was injured.
Brandon Pettigrew has not been cleared to practice while recovering from a torn knee ligament late last year and might not be healthy enough to start the season in five weeks. Tim Wright, another veteran, had a season-ending knee injury earlier this year.
The top tight ends left standing might be Cole Wick, an undrafted rookie from the University of the Incarnate Word in Texas, and journeyman Matthew Mulligan, who has 17 career catches since making his NFL debut in 2009.
The other tight ends on Detroit's roster are: Orson Charles, Adam Fuehne and Ben McCord.
Mulligan said it was "devastating," to see a teammate go down with an injury in practice.
"All of us are going to have to step up," Mulligan said. "Ebron is an incredible player."
The Lions may have to use more formations with three or four receivers and one of them will not be Johnson. He left the Lions and the league earlier this year after nine seasons.
Detroit's top receivers are Golden Tate and a pair of newcomers, Marvin Jones and Anquan Boldin, along with TJ Jones, who was taken out of the mock game after hitting the turf hard on an overthrown pass.
"I just dove and someone landed on top of me," Jones said. "Nothing. I'm good. All good to go."
Jones refused to say if he went through the concussion protocol.
"I'll leave that all to the trainers and coach (Jim) Caldwell to talk about the details of everything, but I'm feeling great," Jones said.
Caldwell spoke to reporters before the mock game, the only time he was scheduled to be available, and declined comment after the practice.