Joe Marler will miss the start of the Six Nations after he was handed a six-week suspension at an independent disciplinary hearing.
England were handed a further blow with the confirmation that Ben Te'o will also miss the beginning of the tournament with an ankle injury that has kept him out since October.
Marler was sent off in the 58th minute of Harlequins' 30-29 defeat to Sale Sharks in the Aviva Premiership on Saturday for striking TJ Ioane with his shoulder.
The loosehead prop will miss England's first two matches, against Italy and Wales, with his ban set to expire on February 20.
The chairman of the disciplinary panel Philip Evans QC said: "The panel considered that the player's previous record was such that it required an additional period of suspension of one week.
"However, because of his plea, his conduct since the incident took place and other personal mitigation, the panel allowed some reduction".
Marler has a chequered disciplinary history, and he was forced to miss England's autumn international against Argentina in November after receiving a ban for striking an opponent with an elbow.
The 27-year-old's absence could cause Eddie Jones a problem, as fellow loosehead Ellis Genge is currently injured after undergoing shoulder surgery.
Mako Vunipola is fit, but Jones may be forced to hand a call-up to Bath's uncapped Beno Obano, who was part of England's training camp in Brighton last week.
Te'o's absence was confirmed by his club side Worcester, who said that they expected him to be out for a further four weeks.
Sale flanker Ioane has also been banned after pleading guilty to striking Marler in the 53rd minute of the game against Harlequins - just five minutes before Marler was sent-off for striking him.