Crotty is set to be on the sidelines for the opening two rounds after damaging ligaments in his thumb.
Fruean on the other hand tore his pectoral muscle in the gym at the end of last year. Following surgery he is now set to make a return in April.
Blackadder has plenty of sympathy for Fruean after his latest injury setback and is now working on a solution in midfield prior to the Crusaders’ first clash with the Chiefs on February 27.
Nemani Nadolo, Kieron Fonotia, David Havili and new recruit Sean Wainui are all potential options.
“[Fruean] is pretty tough, he’s had to deal with these things before. He takes it in his stride,” Blackadder told Stuff.
“He was just doing weights in the gym, it was at a testing level. It’s really disappointing to lose a guy (who was) not out in the field of battle.
“We’ve got a few injuries we could focus on but we’re not. We’re just going to focus on the guys that are fit and ready to go.
“I’m still really confident the way we’ve got enough depth to cover those positions.”