It's understandable if Cleveland Browns WR Mohamed Massaquoi is a tad sensitive about concussions. They have certainly limited his growth as a player. So perhaps he was in denial when he tweeted that he came out of the game Friday night in Detroit for "precautionary" reasons after taking a blow to the head on the team's first play from scrimmage.

Coach Pat Shurmur plainly stated following the victory that Massaquoi had a concussion, which would be the third of his career. So after Shurmur heard that he was contradicted by his starting receiver, he wasn't exactly turning cartwheels.

"I told you what happened, and that's what happened," Shurmur stressed to the media. "I don't like [the players tweeting]. That's my policy. I encourage them not to and [hope] they don't, but you can't totally harness social media. I encourage them to be professional and not talk about Browns business."

Shurmur praised Massaquoi last week as the most improved player in camp over the past year. Team president Mike Holmgren predicted a breakout season for the third-year wideout, who showed promise as a rookie until taking a jarring blow from Steelers LB James Harrison and suffering the first of what is now three career concussions.

The Massaquoi injury simply adds to a long list for the Browns. Fifteen players missed practice Sunday, including Massaquoi, TE Jordan Cameron (back), DT Scott Paxson (knee), and CB Dimitri Patterson (ankle), all of whom were hurt against the Lions. Shurmur declined to reveal the extent of any of the injuries.

Out for extended periods are LB Chris Gocong (season-ending Achilles surgery) and DT Phil Taylor (pectoral), who will miss at least six regular-season games. FS Usama Young, MLB D'Qwell Jackson, TE Benjamin Watson, DE Frostee Rucker and RB Trent Richardson are also sidelined. Richardson underwent arthroscopic knee surgery last Thursday, but could return in 2-3 weeks.

The spate of injuries could throw rookies into the fire quicker than anticipated. DT John Hughes started against the Lions and has received extended reps in practice with the first team. LB James-Michael Johnson could start the regular-season opener against the Eagles with Gocong out and strong-side LB Scott Fujita facing a three-game suspension for his alleged role in Bountygate. WRs Josh Gordon or Travis Benjamin have the inside track on replacing Massaquoi in the starting lineup, though the former was considered a possibility before the injury.

Among the most impressive rookies has been CB Trevin Wade. Wade has worked both outside and in the slot as a replacement for Patterson. A possible four-game suspension for CB Joe Haden could also result in immediate playing time for Wade. Haden was reportedly informed by the league that he failed a drug test.

"I'm just going with the flow," Wade said. "Wherever they're putting me, I'm trying to pick up my game so if they put me into the fire, I'll be ready. I just want to play good technique and anticipate what's coming. I'll be fine. It was pretty crazy the first snap [in Detroit], but after the first series I got comfortable. If I get an increased number of reps, I have to make the most out of those increased reps."

Wade was among the standouts against Detroit. He successfully defensed two passes and made three tackles. He is battling second-year cornerback Buster Skrine for playing time. Skrine struggled with talented and physical Lions WR Calvin Johnson.

Stay dialed in on the Cleveland Browns @CBSSportsNFLCLE on Twitter throughout the season with on-site updates from CBSSports.com RapidReports correspondent Marty Gitlin.