Their opponents have already announced the first leg of that tie will take place at their Owlerton base on Thursday (September 17), but Panthers chiefs stress they have not agreed and will not agree to race on that date.
They face being without three riders - Barker, Thomsen and Emil Grondal - due to overseas commitments in addition to captain Ulrich Ostergaard, who recently won the Premier League Riders’ Championship at the track, being ruled out for the rest of the season due to injury.
Joint team boss Carl Johnson said: “We have made our position known regarding the staging of the first leg and we hope there will be further developments in the early part of this week.
“We have three riders away due to other meetings on the continent and we do not feel we should be forced to ride without our best team.
“We have worked so hard for six months to get into this position and we do not want that to go to waste due to having to race without important riders.
But why should Sheffield not ride on their normal race night as Peterborough are missing riders? Where are the missing 3 riding?