The Melbourne Rebels have again let a Super Rugby Pacific halftime lead slip to fall to the defending champion Crusaders 43-27 in a brutal clash.

In their last outing at AAMI Park, the Rebels led the Blues at the break before the visitors blew them away in the second half.

While Friday night's match was a tighter affair, Melbourne's 12-point halftime lead evaporated with the Crusaders running in four second-half tries.

It was a disappointing end to a memorable week for the club, who were looking to celebrate new deals for head coach Kevin Foote and his two assistants.

It was also a huge blow for the hosts, who entered the match in 10th spot and in dire need of wins.

The Crusaders have battled a huge injury toll but were still fourth heading into the contest with star playmaker Richie Mo'unga turning out for his 100th Super cap.

The lead changed hands three times in the second half but the Crusaders managed the game better despite some ferocious Melbourne defence.

The visitors had all the ball early but the Rebels showed desperation to keep them out until the 11th minute, when Braydon Ennor sent a long pass out to winger Macca Springer.

To the home side's credit they hit straight back with skipper Brad Wilkin diving across the line from the back of a ruck.

And they were in again three minutes later when No.8 Vaiolini Ekuasi scooped up the ball, lost by Crusaders centre David Havili after a big hit by Josh Canham.

Ekuasi, who also extended his Rebels deal this week, had to run 90 metres to touch down.

Halfback Ryan Louwrens then got amongst the spoils for Melbourne to take a 24-12 lead to the sheds.

They were notably wary after their halftime lead over the Blues turned into a 54-17 loss.

And their worst fears were realised with two early second-half tries seeing the Crusaders take a 26-24 lead in the 63rd minute.

The Rebels weren't rattled this time and went ahead again through a Reece Hodge penalty kick.

But the Crusaders kept coming and reserve hooker Ioane Moananu shrugged off defenders to storm over.

A Mo'unga penalty gave his team a nine-point buffer and then he set up a try for reserve back Dallas McLeod.

The visitors rubbed further salt into the wound with an 82nd-minute score to also collect a bonus point.

CRUSADERS 43 (TRIES: Springer, Havili 2, Grace, Moananu, McLeod CONS: Mo'unga 5/6 PENS: Mo'unga 1/1)

REBELS 27 (TRIES: Wilkin, Ekuasi, Louwrens CONS: Hodge 3/3 PENS: Hodge 2/2)

REBELS (1-15): Matt Gibbon, Alex Mafi, Sam Talakai, Josh Canham, Trevor Hosea, Josh Kemeny, Brad Wilkin, Vaiolini Ekuasi, Ryan Louwrens, Carter Gordon, Monty Ioane, Stacey Ili, Reece Hodge, Lachlan Anderson, Andrew Kellaway

RESERVES: Jordan Uelese, Cameron Orr, Pone Fa’amausili, Angelo Smith, Daniel Maiava, James Tuttle, Lukas Ripley, Joe Pincus 

CRUSADERS (1-15): Joe Moody,  Brodie McAlister, Tamaiti Williams, Scott Barrett (c), Sam Whitelock, Dom Gardiner, Tom Christie, Christian Lio-Willie, Mitchell Drummond, Richie Mo'unga, Macca Springer, David Havili, Braydon Ennor, Pepesana Patafilo, Fergus Burke

RESERVES:  Ioane Moananu, Finlay Brewis, Seb Calder, Quinten Strange, Cullen Grace, Willi Heinz, Jack Goodhue, Dallas McLeod

Referee: Ben O'Keeffe

Assistant Referees: Stu Curran, Jackson Henshaw