Osborne has made himself available for Fiji during the June test window, thereby ruling himself out of ABs contention.
The wing, who has trained with the All Blacks, said: "I have been honoured to spend time in the All Blacks environment but am very proud of where I come from and have decided to commit myself to the Fijian team. It's an exciting new challenge that my family and I are looking forward to."
Osborne's decision to commit to Fiji means he will play overseas when his Highlanders contract is up next year.
The Crusaders got off to a false start yesterday when the plane they were on returned to Christchurch due to high winds in Otago. Instead of a 40-minute flight, the squad had to travel to Dunedin in four mini-buses, a journey of about four hours.
Their travel drama will probably be music to the ears of Joseph, who said of the game: "[The] game doesn't come any better than this - a match-up with one of the best teams in the competition, in-front of a sold out home crowd. This is what our boys get up and play for."
Highlanders chief executive Roger Clark was rapt with the 23,336 crowd set to show for the game, the first time the franchise has sold out Forsyth Barr Stadium.
"We are overwhelmed with the support of our fans down here in Dunedin," Clark said. "This is outstanding and we can't wait to see everyone and put on a great show."