Ostergaard was in brilliant form for the Premiership title challengers until suffering back and wrist injuries while riding for Glasgow in Edinburgh last month.
Ostergaard said: “Very gutted to say a check up at hospital didn’t show my injuries will heal up before season it over so have told both my clubs I can’t resume in 2021
“My three broken bones in my back back need at least 10 more weeks in a cast which means I can only walk and lay down, before physio and more training can be added.
“My head, broken wrist and ribs will be ok soon. A massive thanks to all my sponsors and supporters for their messages over the last few weeks
“I can assure I will fight hard over the next few months and the winter to be fully fit for 2022 as this season for Peterborough Panthers Speedway and Glasgow Tigers Speedway been the most enjoyable I have had for years.”
Panthers have been operating rider replacement for Ostergaard as they will in tonight’s Premiership meeting at King’s Lynn.