The Crusaders became the third New Zealand side to reach the last four, after the Waikato Chiefs fended off the Queensland Reds 29-20 in Hamilton earlier on Saturday.
Already decimated by injuries through the regular season, the Crusaders were down to 13 men in the last 10 minutes when fly half Richie Mo'unga (29) limped off, joining lock Zach Gallagher (21), flanker Ethan Blackadder (28) and others already ruled out.
Fortunately, the home side had built up a 42-8 lead by that stage after running in six tries.
Willi Heinz (36) added a seventh five-pointer in the last minutes as the undermanned Crusaders refused to concede.
"Very pleased with how the boys played tonight," said Crusaders captain Scott Barrett (29). "To finish with 13 men... we covered well."
Beaten by the Crusaders in last year's championship final at Eden Park, the Blues thrashed the New South Wales Waratahs 41-12 in their home quarter-final on Friday.
The Blues will now have to pull off Super Rugby's 'Mission Impossible' in the rematch in Christchurch, where the Crusaders have never lost a play-off.
The Crusaders, hunting a seventh championship trophy in seven years to send off departing head coach Scott Robertson, stretched their winning streak in Christchurch to 28 play-offs against the Drua.
Having upset the Crusaders in Fiji earlier in the season, the Drua turned up to Rugby League Park with hope of at least pushing the hosts.
But they were soon reeling as the Crusaders racked up four converted tries in the opening 33 minutes.
The Chiefs will return to Waikato Stadium next week to play the winners of the ACT Brumbies and the Wellington Hurricanes, who clash in the last quarter-final in Canberra on Saturday.
A late try to Pita Gus Sowakula (28) and the unerring boot of Damien McKenzie (28) sank the Reds, who had led at the 70th minute and threatened to pull off a big upset.
McKenzie slotted in five penalties and two conversions in a flawless night off the tee.
The Chiefs' hulking, bearded number eight Sowakula sealed the win with a try in the 75th minute, plucking the ball out of a ruck and planting it next to the left post.
"We came up against a really tough Reds side. To be fair, that's what we expected," said Chiefs skipper Sam Cane (31).
"It was an arm-wrestle, we had to grind it out."
Brad Thorn (48) confirmed he had overseen his last match as Reds coach after six years in the role.
"It's time for a break," said the dual code international.
The Chiefs had only one other try-scorer, with livewire winger Emoni Narawa (23) crossing at the left corner seconds after the half-time siren to put the hosts 16-10 up at the break.
The only team to beat the Chiefs in the regular season, the Reds were gallant in defeat.
Winger Suliasi Vunivalu (27) put his hand up for Wallabies selection with a terrific individual match, scoring the opening try in the ninth minute and grabbing another on the hour mark.
No Australian team has ever won a Super Rugby play-off in New Zealand, and that streak will stretch into another year.
Check out the game summary from the Crusaders' win with Flashscore.
Later, The ACT Brumbies prevented a New Zealand shut-out in the semi-finals of Super Rugby Pacific by defending to the death in a 37-33 cliff-hanger against the Wellington Hurricanes in Canberra.
Camped on their try-line, the Brumbies held off wave after wave of attacks for nearly five minutes after the siren before Hurricanes skipper Ardie Savea made a dive under the posts, only to be denied a try by the desperate hand of replacement loose forward Luke Reimer.
With the home crowd holding their breath, the television match official reviewed Nic Berry's on-field decision then confirmed it, leaving the Brumbies celebrating victory and Savea crushed.
The Hurricanes skipper argued that he had grounded the ball.
"As much as I disagree, that's just the way it goes," said the emotional flanker. "I scored it, brother. Initially, I scored it anyway.
"It is what is it is. I'm gutted. At the end of the day you can't change it."
The Brumbies' reward will be a tough trip to Hamilton to meet the table-topping Waikato Chiefs, who earlier battled to a 29-20 win over a spirited Queensland Reds team.