The Crusaders were given an almighty scare before running in two tries in the final nine minutes to overcome a plucky Western Force outfit 42-30 in a thrilling Super Rugby encounter in Perth on Saturday night.

The Force led 30-28 with just nine minutes remaining courtesy of two tries to fullback Cameron Shepherd and the hot boot of James O'Connor, who nailed five-of-five penalties.

But the Crusaders hit back with a vengeance in a frantic finish, with tries to hooker Corey Flynn and halfback Kahn Fotuali'i getting the seven-times champions over the line.

The five-try bonus-point win lifted the Crusaders back to within three points of the Blues in the race to finish top in the New Zealand conference.

Force flanker David Pocock was sensational in his first game back from a knee injury, earning some important penalties in the second half as the home side threatened to steal the win.

The Crusaders made a blistering start to the match, with fullback Israel Dagg nailing a brace of tries within eight minutes as the visitors opened up a 12-0 lead.

Winger Sean Maitland set Dagg up for the first with a nifty inside pass after fending off a Ben McCalman tackle.

But it was Dagg's pure class that got him the second, shaking off a weak David Smith tackle, brushing away James O'Connor and Richard Brown before wrong-footing Shepherd to score under the posts.

The hot boot of O'Connor kept the Force within striking distance as the home side closed the gap to 15-9.

And the Force hit the lead in the 29th minute when Shepherd scored after a bizarre sequence of events.

First, a promising Force foray broke down, allowing Crusaders inside centre Sonny Bill Williams to make a clever break.

But just as the Crusaders seemed set to score with a glut of numbers out wide, a dropped pass opened the door for the Force.

Smith pounced on the loose ball and made some valuable metres before dishing off to O'Connor, with the ball then finding itself in the hands of hooker Nathan Charles and five-eighth Willie Ripia before an open Shepherd strolled through untouched.

The lead lasted a mere minute, with Israel Dagg finding a gap between Nathan Sharpe and Pek Cowan before dishing to Williams for the easiest of tries.

A late O'Connor try closed the deficit to 22-19 at half-time, and the game swung the Force's way when returning Crusaders skipper Richie McCaw was sinbinned for repeated infringements in the 47th minute.

A double piece of O'Connor magic - when he followed up a clever grubber kick with a fierce tackle on Williams 20 seconds later - led to Shepherd's second try in the 53rd minute, giving the home side a 27-25 advantage.

The margin stretched to five when O'Connor nailed his fifth penalty, but from there it was all the Crusaders as they scored the final 17 points of the match to secure the win.

"I thought the first 30 minutes was like a training exercise for them," Force coach Richard Graham said.

"I thought we kicked poorly. With (Zac) Guildford, (Sean) Maitland and Dagg exceptional at the counterattack, it hurt us."

Crusaders coach Todd Blackadder said his side's ill discipline allowed the Force to stay in the contest.

"They played smart rugby, they played the game in our half and we gave penalties away and that kept them in the game," Blackadder said.

"Any mistakes we made they capitalised on it."

Brought to you by AAP © 2024 AAP