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Ryan Crotty is keen to add to his 15 Test caps for New Zealand, the Crusaders midfield back acknowledging the "opportunity" with key All Blacks players having exited the Rugby World Cup-winning fold.

Crotty missed the cut for the World Cup having featured against Argentina at AMI Stadium during the Rugby Championship, but midfield Test spots will be up for grabs in 2016 with Ma'a Nonu and Conrad Smith having joined the exodus to France and Sonny Bill Williams concentrating on Sevens.

"There's opportunity there and it's exciting, and I'm sure every other midfielder around the country is thinking the exact same thing," Crotty said. "It's important I work really hard and play the best I can for the Crusaders, and opportunity comes on the back of that."

Crotty, meanwhile, said that Todd Blackadder's decision to step down as Crusaders coach after the 2016 season had provided added motivation for the campaign. The 2016 Super Rugby season will be Blackadder's eighth and last in charge of the Crusaders, the most successful franchise in the competition's history, but he hasn't been able to add to their seven championships.

Crotty said it came as a surprise when Blackadder announced last month he would be stepping down.

"It's kind of sad - he's been bloody successful without getting a title to his name," he said. "That might be a bit of motivation for a few of the guys to try to really send him out the way he deserves."

The Crusaders will have to achieve that without two of their greats - Richie McCaw and Dan Carter. McCaw has retired after leading the All Blacks to their second successive World Cup triumph, while Carter has headed to France after his man-of-the-match performance in the final.

"It's hard to deny that those two guys will leave a bit of a gap," Crotty said.

"They're two of the best players that rugby has ever seen, but, in saying that, we have guys who can step up.

"We've got Matt Todd and he's the most underrated No.7 I've seen and it's a good opportunity for a young 10 to step up." Todd is an obvious replacement for McCaw, but there will be a less familiar face at first five-eighth with Colin Slade and Tom Taylor joining Carter at French clubs. Canterbury's Richie Mo'unga, Fiji international Ben Volavola, and former Chiefs pvot Marty McKenzie provide the playmaking options next year.