Saints are facing a second row shortage for some crucial Gallagher Premiership games after hearing Api Ratuniyarawa will be suspended for four weeks.
The Fijian lock was sent off for dangerous play at a ruck during the defeat to London Irish at Franklin's Gardens last Friday night.
Ratuniyarawa's shoulder made contact with the head of Irish prop Harry Elrington, prompting referee Tom Foley to produce a red card in the 50th minute of the match.
Ratuniyarawa subsequently appeared before a disciplinary panel on Tuesday night and was given a four-week ban by an independent disciplinary panel.
It means he will miss the matches against Bristol Bears, Exeter Chiefs, Saracens and Worcester Warriors.
And it leaves Saints very light at lock as they are already without David Ribbans, who suffered an ankle injury earlier this month, and England players Courtney Lawes and Alex Moon.
That means the likes of youngster Alex Coles and Lewis Bean will have to hold the fort in some big matches if Moon doesn't get released by England during the Six Nations.
Ratuniyarawa had pleaded not guilty at his hearing, but the panel did not accept his take on the incident.
Independent panel chair Charles Cuthbert said: “The player did not accept that he had committed an act of foul play by dangerously charging in to the ruck. He argued that he had bound on to the London Irish player. This was not accepted by the panel after reviewing the footage.
“The panel found it was a reckless action.
"While the panel were satisfied that there was no intent to cause injury, his shoulder did make contact to the face of the London Irish player who confirmed he suffered no injury as a result.
"The mandatory mid-range entry point applies where there is contact with the head and the panel found no factors to merit a top-end entry point.
“The player was allowed mitigation for his clear disciplinary record over a long professional career at a high level.
"He apologised both on and off-field to the London Irish player involved and his own team, and is engaged in community activities and coaching.
"He was allowed two weeks in mitigation and is therefore suspended for four weeks.”