Webster, who pleaded not guilty to the Grade B offence, was also fined £300 after the RFL Disciplinary Committee ruled he had used his body to twist and apply pressure to Riley’s leg and moved his opponent’s lower leg and knee joint in an abnormal direction in a way that involved an unacceptable risk of injury.
The hearing was told that Webster had received a formal caution over a similar offence in April 2010.
The Disciplinary Committee also fined Wakefield Trinity Wildcats hooker Julien Rinaldi £500 after finding the French international guilty of making a tackle which placed undue pressure on the shoulder joint of Catalans Dragons prop David Ferriol.
Rinaldi had been charged with a Grade B offence but the committee downgraded the tackle to Grade A and issued the player with a written warning about his future tackling technique. The tribunal also took into account Rinaldi’s previous exemplary record.