CLEVELAND (AP) — Browns offensive lineman Ryan Miller returned to the team’s training facility on Sunday and began the NFL’s concussion protocol after being knocked unconscious during practice.

Miller was rushed to the Cleveland Clinic on Saturday after his frightening injury during a routine blocking drill brought the Browns’ indoor workout to a standstill. The 6-foot-7, 320-pounder, who was released from the hospital after a few hours, will be monitored by the medical staff and must pass a series of tests before he can return to the field.

Browns coach Rob Chudzinski said he visited Miller on Saturday night.

Miller was taking part in one-on-one blocking drills inside the team’s indoor field house when he dropped after making contact with his helmet. He lay motionless for several minutes, and his teammates huddled around him in prayer as he was immobilized and strapped to a backboard. The Browns initially feared Miller had suffered a devastating injury, and were relieved to learn he was responsive and moving his limbs.

Browns linebacker D’Qwell Jackson said the only other time he experienced anything as scary was when former Browns kick returner Josh Cribbs was knocked out last season in Baltimore.

“I’ve only witnessed it a few times and anytime that happens you just pray and just hope for the best and hope everything is OK,” said Jackson. “I’ll tell you what, it made everyone realize that at any moment anything can happen.”

The Browns drafted Miller in the fifth round out of Colorado last year. He played in eight games as a rookie and is expected to begin this season in a backup role behind Pro Bowl starter Joe Thomas and Mitchell Schwartz.

Cleveland has experience in dealing with concussions. Along with Cribbs, former quarterback Colt McCoy sustained a head injury at Pittsburgh two years ago that prompted the league to change its in-game handling of concussions.

NOTES: The Browns practiced in full pads — they only wore shoulder pads Saturday — for the first time during Sunday’s fourth day of training camp and a crowd of 4,466 came out to hear some popping. The team said it was a single-day attendance record in Berea. Fans were unable to see Saturday’s workout because it was moved inside by rain. … RB Montario Hardesty sat out with a hamstring injury and worked on the side with trainers. Chudzinski said Hardesty, who rushed for 272 yards last season, is day-to-day. … DE Desmond Bryant didn’t practice because of back spasms. He’s also day-to-day. … Tashuan Gipson, trying to win a starting job at safety, sustained a shoulder sprain after colliding with WR Josh Gordon. Chudzinski doesn’t think the injury is serious.