Collins has started six league games for Worcester this season
Sale Sharks have announced former Worcester flanker James Collins will not be joining the club after failing to recover from a previous injury.
Collins has not played since suffering concussion against Nottingham in March.
The 25-year-old suffered the injury three days after agreeing to join Sale and has been unable to take part in pre-season training.
"We have to consider the players' welfare," said executive director of sport Steve Diamond.
Sharks chief executive
“We are sorry that this situation has arisen and extend to James our best wishes for his long-term future”
"It's a big disappointment for James and for Sale Sharks. We wish him well in his future career."
England Sevens international Collins is now out of contract after leaving Warriors but a return to playing has been described by Sale as "some way off".
He had agreed a two-year contract at Edgeley Park.
"We are sorry that this situation has arisen and extend to James our best wishes for his long-term future," added Sharks chief executive Mick Hogan.