Salford winger Justin Carney could face a suspension of eight or more games after he was accused of racially abusing a Toronto Wolfpack player.
Carney, 28, was sent off by referee Jack Smith in the 26th minute of the Super League club's Challenge Cup fifth-round win on Sunday.
The Rugby Football League have charged Carney with a Grade F offence, for verbal abuse based on race or colour.
Salford are also investigating events leading up to the sending-off.
The Grade F charge is the most severe category of offence and carries a penalty of at least eight games, or a fixed time period of suspension, if a player is found guilty.
Australian Carney, who is in his second season with Salford, does not have the option of entering an early guilty plea.
The Challenge Cup tie brought an end to Toronto's first run in the competition, with the Canadian third-tier side having made their debut in English rugby league in the third round of the competition in April.
It was the first competitive defeat that the Wolfpack, who have won all five of their League 1 matches in 2017, had suffered.
Meanwhile, Toronto forward Jack Bussey will face a hearing after being charged with a Grade B offence of striking with his elbow or forearm and team-mate Bob Beswick has been given a caution for striking with his knees in the same game.
Hull FC prop Liam Watts has been charged with a Grade B high tackle following his sending-off in his side's 26-24 Super League win over Castleford, which could result in a one or two-match ban if he is found guilty.
Huddersfield full-back Darnell McIntosh (punching) and Warrington forward Joe Philbin (tripping) face Grade A charges.