Controversy swirled during Game 6 between the Pittsburgh Penguins and Washington Capitals on Monday night, after Pens captain Sidney Crosby continued to play despite appearing to suffer another head injury.

The incident occurred late in the first period when Crosby - who was diagnosed with a concussion in Game 3 - got tangled with Braden Holtby and tumbled violently into the end boards.

After questions quickly surfaced as to why Crosby wasn't pulled from the game by the league-mandated concussion spotter to undergo tests, NHL deputy commissioner Bill Daly provided an explanation Tuesday.

"Depending on the mechanism of the injury, 'slow to get up' does not trigger mandatory removal," Daly told USA Today Sports. "The protocol has been interpreted literally to mandate a removal. 'Ice' as compared to 'boards' is in there for a reason. It's the result of a study on our actual experiences over a number of years. 'Ice' has been found to be a predictor of concussions - 'boards' has not been."

Regardless of what the rule book states, the decision to leave Crosby in the game and the league's questionable subsequent response have further damaged its reputation for dealing with head injuries.

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