DENVER -- Miami Dolphins wide receiver Chris Chambers had to be helped from the field Sunday night after taking a vicious hit to the head from Denver safety Kenoy Kennedy in the second quarter.

The initial diagnosis was that he had sustained a concussion. Chambers did not return to the game.

A high-ranking league source told ESPN.com's Len Pasquarelli late Sunday night that Kennedy "certainly" faces substantial sanctions for his hit on Chambers.

Chambers went up for a high pass from Jay Fiedler and appeared to have caught it until he was hit in mid-air by Kennedy, and the ball came free.

Officials issued a personal-foul penalty against Kennedy for the helmet-to-helmit hit.

Chambers lay motionless on the field for several seconds.

Kennedy appeared to try to apologize to Chambers as the receiver left the field, but he was pushed away by Dolphins tight end Randy McMichael.

A third-year veteran, Kennedy was cited twice earlier this season for plays that went beyond the scope of normal contact, including a $10,000 fine last week for a helmet-to-helmet hit on San Diego fullback Fred McCrary in last week's victory over the Chargers.

The league source termed the hit "blatant" and "a textbook example" of illegal helmet-to-helmet contact. He also noted the two earlier fines that Kennedy had drawn through the first five weeks of the 2002 campaign. "I think it's fair to say there's a pattern here," he said.

Kennedy, 24, was fined $7,500 last month for a hit on St. Louis Rams wide receiver Isaac Bruce in the season opener. In a letter sent to Kennedy last week, league officials apprised the safety that further incidents could result in his suspension.

Information from ESPN.com's Len Pasquarelli and The Associated Press was used in this report.