Reeves fractured his left leg in a collision with receiver Andre Davis when both were going for a pass in the end zone. Reeves, who signed as a free agent in 2008, is expected to be out 6 to 8 weeks.
Myers sustained a high ankle sprain and will be out indefinitely. Both players attended practice wearing walking boots in the afternoon.
Myers, who started all 16 games last season after being traded by Denver, was injured early in a practice coach Gary Kubiak called "sloppy." He was taken off the field on a cart.
"We're checking the severity of that," Kubiak said of Myers' injury. "But obviously he's going to miss some time."
Kubiak was unhappy with all aspects of the practice.
"It [Myers' injury] happened on a sloppy play," Kubiak said. "We were sloppy as a team. I didn't like much of anything I saw this morning."