Vintage this was not, but the Crusaders eventually survived a scare to subdue the committed Reds and book a home semifinal next week.
The Crusaders were shaky, rattled even, for 60 minutes of Friday's quarter-final in Christchurch, before easing out to a comfortable victory after being sparked into life by their lethal backline threats - Richie Mo'unga, Will Jordan, who was the most influential player on the park, Leicester Fainga'anuku and Sevu Reece.
The four-tries-to-two victory came at a significant cost for the All Blacks and Crusaders, though, with impressive loose forward Ethan Blackadder departing in the 62nd minute with a concerning wrist injury.
After a superb performance from openside flanker at the breakdown and with ball in hand, Blackadder was in serious pain when he left the field and is likely to face an extended stint on the sideline.
Trailing 16-8 at halftime the Reds should have snaffled the lead early in the second spell, only for Lawson Creighton to push a penalty wide. The one-point deficit was as close as they would get but Brad Thorn's men gave as good as they got for the vast majority of this contest, coming much closer than many expected.
While they progress to the final four the Crusaders won't be satisfied with their lack of accuracy. In many respects this performance continued a frustrating trend after similar skill-based issues blighted their patchy 28-15 win against the Reds last week.
The Reds were rank outsiders for good reason. They are now 0-6 against New Zealand teams this season, losing five of their past six games to all comers, and they last won in Christchurch 23 years ago. Yet they seriously troubled the Crusaders, despite being dominated in the scrums.
Wallabies loose forward Harry Wilson was among the Reds best while fellow flanker Liam Wright applied consistent breakdown pressure to disrupt the Crusaders flow.
When Reds wing Filipo Daugunu scored from a superb lineout set move just after halftime to bring the visitors within one point, it was anyone's game.
Mo'unga, in his return from a two-game absence with a fractured finger, was largely quiet but he skipped over for a vital try after the Crusaders maul was shut down and their scrum earned them another chance.
Reece's try, as he jinked off his right foot to find space after a brilliant counter from Jordan and Fainga'anuku, blew the margin out and replacement prop Tamaiti Williams finished the job with an unstoppable try off the bench.
Knockout matches bring a different level of tension and nerves. Both were evident from the Crusaders.
Coach Scott Robertson's men struck early through Jordan after David Havili and Reece combined from a slick lineout move but as was the case last week, the Crusaders' fundamental skills were far from clinical.
While he played a key role in a dominant scrum that gained three penalties, All Blacks prop George Bower twice spilled the ball in contact and Argentine loose forward Pablo Matera made another mistake to thwart momentum.
Two overthrown lineouts also proved costly. The Reds made the most of the second, with Wallabies midfielder Jordan Petaia skinning Jack Goodhue on the outside break and Suliasi Vunivalu pushing off Jordan to score in the corner and bring the locals within two points.
The Crusaders were denied two further first-half tries with All Blacks hooker Codie Taylor held up from a maul and Fainga'anuku's strike on halftime ruled out for an earlier Jordan error.
In a sign of respect, and a nod to the Reds' improvement from last week, Mo'unga knocked over three penalties to ease mounting pressure.
Two tries from the Crusaders in the final 15 minutes put a decidedly different spin on the complexion of this match.
The Crusaders have now won five successive games. Yet whoever travels south for next week's semifinal will not be intimidated by the nature of this performance.
Crusaders 37 (Will Jordan, Richie Mo'unga, Sevu Reece, Tamaiti Williams tries; Mo'unga 4 cons, 3 pens)
Reds 15 (Suliasi Vunivalu, Filipo Daugunu tries; Lawson Creighton con, pen)