The 13-times champions ran in eight tries, including three in an eight-minute blitz before halftime, to extend their perfect record in Christchurch playoffs to 33 games going back to 1998.
The Aucklanders made the better start and it was only after visiting number eight Malachi Wrampling received a red card in the 19th minute that the Crusaders were able to take charge.
The Blues will still take their place in the semi-finals as the highest-ranked playoff losers if the Waikato Chiefs beat the Queensland Reds in Saturday's late game.
That would send them to Wellington next week to take on the top-seeded Hurricanes, who underlined their title credentials with a record 66-12 demolition of the ACT Brumbies on Friday.
The Blues were coming off three straight losses but came out firing and deservedly took the lead in the third minute when scrumhalf Sam Nock went over from a well-worked move off an attacking lineout.
Sevu Reece soon scored his 74th Super Rugby try to level up the scores against the run of play but the Blues were down to 14 men seven minutes later after Wrampling's shoulder clattered into the head of Leicester Fainga'anuku.
Fullback McNicholl took advantage with his first try almost immediately but in-form Blues flanker Anton Segner levelled up the score just before the half-hour mark.
The next 10 minutes were all Crusaders, however, with skipper David Havili, winger Chay Fihaki and flyhalf Taha Kemara crossing to give the reigning champions a commanding 33-14 lead at the break.
Havili sent McNicholl in for his second try five minutes after the restart to extend the lead to 40-14 and give the Blues a mountain to climb.
They scored tries through Xavi Taele, Payton Spencer and Caleb Clarke but McNicholl completed his hat-trick and replacement hooker Manumaua Letiu also crossed to maintain a comfortable cushion for the Crusaders.