The Melbourne Rebels admit they "got their pants pulled down" by the Crusaders in a 39-0 Super Rugby Pacific reality check.

In Christchurch, the visitors were never in the contest and were absolutely monstered up front by a side that came into Friday's fixture on the bottom of the ladder.

The fourth-ranked Rebels had won their previous three games to insert themselves in the finals frame, but were given a harsh reminder of the difficulties of winning games in New Zealand.

Their scrum was completely decimated in the first half, to the point that coach Kevin Foote replaced the entire front row before the break.

Matt Gibbon, Alex Mafi and Sam Talakai were hooked on the half-hour after a shift that saw them concede three penalties and lose multiple scrums against their own feed, including one where the Crusaders drove them back into their own in-goal.

The bench group - including Wallabies talents Taniela Tupou and Jordan Uelese - solidified things in the short term, but were eventually worn down by the hosts' power.

Talakai conceded it had been an embarrassing night.

"They're hurting and they came out and they fought for everything," he said.

"It showed up front, they got on top and they stayed on top, so disappointing for us.

"There are some quick fixes, but at the end of day we've got to look in the mirror, we were probably looking too far ahead.

"We came here and we got our pants pulled down ... we're gonna go back and review hard."

Crusaders No.8 Christian Lio-Wllie and flanker Cullen Grace put their side 10-0 clear within 17 minutes, but the floodgates really opened late with three second-half tries against a broken Rebels outfit.

The Rebels' Ryan Louwrens kicks under pressure from Crusaders captain Scott Barrett.

Perhaps things could have been different if Rebels forward Josh Kemeny had grounded a short-range effort on the stroke of halftime, but he lost control of the ball diving for the line in what was a chance to pull them to within a single score while trailing 10-0.

Instead the Crusaders resumed their dominance after the break, Lio-Willie powering over for a second, before Rivez Reihana knocked over a penalty to put them 18-0 clear on 50 minutes.

Owen Franks, Sevu Reece and Johnny McNicholl cashed in late when the Rebels threw in the towel.

It was just the Crusaders' second win of the campaign, but they immediately jumped into ninth spot to remain a competition factor.

"When they changed the front row there it was going to be a bit of an arm-wrestle when they held us out a couple of times and they didn't lie down, so we had to reset," Crusaders captain Scott Barrett said.

"There were some stern words this week and plenty of hurt over the past few weeks, but it was pleasing to see the boys roll up and put on a performance like that.

"The forward pack started to get into their work. At times this season we've really struggled up front, but the scrum went really well there."