Saints skipper Dylan Hartley has been banned for two weeks for striking Rory Best during last Friday’s defeat to Ulster at Franklin’s Gardens.
Hartley did not receive any punishment at the time of the event, but was put in the dock on the recommendation of citing commissioner Jean-Claude Legendre.
He pleaded guilty at a hearing in Dublin on Thursday and will now face another spell on the sidelines.
Hartley was hit with an eight-week ban earlier this year for biting the finger of flanker Stephen Ferris during England’s clash with Ireland in the Six Nations.
And he will now miss Saints’ return clash with Ulster in Belfast on Saturday as well as the huge Premiership clash with English champions Harlequins at the Gardens a week later.
Hartley is free to play again on December 24, six days before the game against Saracens at stadium:mk.