Saints have issued an update on Rob Horne, stating that the Australian centre sustained an arm injury during the win against Leicester Tigers at Welford Road on Saturday.
Horne was forced off after just 12 seconds of the east midlands derby, having sustained concussion in a collision with Sione Kalamafoni after chasing a Saints kick-off.
He was named captain for the day, but was soon stretchered off after undergoing lengthy treatment on the field.
Horne was taken straight to Leicester Royal Infirmary and remains at the hospital, receiving specialist care for the arm problem.
Saints' update, which was sent out on Sunday evening, read: "Rob Horne remains in hospital this evening having suffered an arm injury during Northampton Saints’ victory at Welford Road yesterday.
"The 28-year old Australian is receiving specialist treatment to his right arm and will continue to be assessed to determine the extent of his injury.
"He wishes to send his thanks to everyone at Leicester Royal Infirmary and for the messages of support he and his family have received."