Calum Clark says he is looking forward to a fresh start after agreeing to join Saracens from Saints.
The flanker will leave Northampton this summer after seven years at the club.
Clark has made 142 appearances for Saints since joining from Leeds Carnegie in the summer of 2010.
He was the club’s players’ and supporters’ player of the season in 2014/15 after a stellar campaign.
But he missed the entirety of last season with a shoulder injury and is currently out with a knee problem.
Clark will be keen to return to action before the end of the season to sign off at Saints before starting his new challenge at the current Premiership and Champions Cup holders.
“I am very fortunate to have played for a great club like Northampton,” said the 27-year-old.
“I’ve had a difficult 18 months on and off the field and I feel like I need a new challenge.
“As ever, I am fully committed to playing to the best of my ability for the remainder of my time at the club.
“I feel very privileged to have been given an opportunity at Saracens.
“They are always a difficult side to play against and I’m looking forward to taking on a new environment and getting a fresh start in the summer.”
And Saracens director of rugby Mark McCall is looking forward to welcoming the back row forward.
McCall said: “Calum is a very talented player and will fit in brilliantly here at Saracens.
“He is still a player with a huge amount of potential and in our opinion he has his best years ahead of him.
“We’re looking forward to welcoming him to the club later this year.”