Ottawa Senators forward Ridly Greig violated an unwritten NHL player code by firing a close-in slap shot into an empty net on Saturday night.

But Toronto Maple Leafs All-Star defenseman Morgan Rielly violated a written rule when he reacted by cross-checking Greig in the head.

The NHL's player safety department announced on Tuesday that it is suspending Rielly for five games for his infraction.

"This is a forceful intentional strike to an opponent's head using his stick as a weapon to exact retribution well after a goal has been scored," the department said in a video.

Rielly had an in-person hearing (via Zoom), so the suspension could have been six games or more. It was the first time that the defenseman had been suspended or fined by the league during his 11-year career. Rielly will forfeit more than $195,000 in pay.

The NHL Players' Association can file an appeal on Rielly's behalf. Commissioner Gary Bettman would rule first and then it could go to an independent arbitrator.

Toronto players took exception to Greig's goal and said it deserved a reaction by the Maple Leafs.

“I don’t think it’s really necessary to go down there and (do a) hardest shot competition into the net,” forward Auston Matthews said.

But the department disagreed with Rielly's approach.

"Rielly approaches Greig for some time and has significant time to engage him in a different manner or ensure this cross-check is delivered solely to the body," it said.

The Maple Leafs will have to find a way to make up for Rielly's absence. They held the first wild-card position in the Eastern Conference heading into Tuesday's games, but the New Jersey Devils and New York Islanders were just four points back.

Rielly leads the team in ice time at more than 24 minutes a game. He leads Toronto defensemen in goals, assists and points, and his 43 points rank fourth on the team.

Detroit Red Wings forward David Perron was suspended for six games earlier this season for a cross-check to an opponent's head on another reaction play. He hit Ottawa's Artem Zub after seeing his captain, Dylan Larkin, lying unconscious on the ice, though Zub was not involved in the hit that injured Larkin. Perron previously had been fined for a retaliatory cross-check.