The 26-year-old Scot, pictured, is unavailable due to having a prior commitment, organised long before the dates of the final were known.
He will also be missing for the Boxing Day clash with Sheffield Steeldogs and the trip to Telford Tigers on December 27.
Elsewhere, defenceman Ross Kennedy could be in line for a return to action after missing the last four games through illness, although Whistle said a final decision will likely be taken before face-off tonight.
“Having Joe out is a big miss for us,” said Whistle. “He has been solid all season and on that line with Jordan Fisher and Ethan Hehir, they have performed a valuable job.
“Ross is feeling much better than he was a couple of weeks back, but we’ll have to see how he is on the day before we make a final decision.”
As expected, Harry Gulliver will dress for the Knights once again as he looks to maintain his impressive scoring record in the competition, so far having scored five times in three games.