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.
"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.
