Bowler Peter Siddle has cancelled his Nottinghamshire deal for 2016 because of a stress fracture in his back.
The 31-year-old Australian was forced to pull out of the second Test against New Zealand after suffering from back spasms and is set to have a "lengthy" spell on the sidelines after surgery.
Siddle had signed a two-year deal to play County Championship and 50-over cricket from this season.
Director of cricket Mick Newell said Notts will sign a replacement.
"It's obviously disappointing, most importantly for Peter himself, and we wish him well for his recovery," Newell said.
"An experienced overseas bowler is a key position for us and we're confident of signing a player of sufficient quality in time for the start of the season."
Siddle took 37 wickets at 31.48 in his previous spell with Notts in 2014.
He has played 61 Test matches since making his debut in 2008, taking an Ashes hat-trick in 2010 and claiming four five-wicket hauls against England.
Cricket Australia physiotherapist David Beakley said: "He will now require a significant amount of time away from the game with a lengthy rehabilitation process.
"While he is laid off with his current back injury, we will take the opportunity for Peter to have exploratory surgery on his left ankle to investigate and treat the cause of his ongoing ankle pain.
"Once that surgery is complete we will have a better idea of his prognosis and likely rehabilitation time frame."