Worcester have signed former South Africa centre Wynand Olivier.
Wales international Jonathan Thomas has been forced to retire from rugby at the age of 32.
Worcester have signed Ireland international lock Donncha O'Callaghan from Munster on a two-year contract.
Bristol flanker Marco Mama has joined Aviva Premiership new-boys Worcester on loan until the end of February.
Aviva Premiership champions Saracens will open the defence of their title at home to the Sale Sharks on October 17.
English clubs say they will allow their players to compete at next summer's Olympic Games as part of Great Britain's Sevens team.
European Challenge Cup holders Gloucester will face local rivals Worcester Warriors in the 2015-16 competition.
Dewi Morris reflects on a remarkable Championship play-off between Worcester Warriors and Bristol.
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