The Western Force were left battered and bruised after conceding seven tries in a 45-17 loss to the Crusaders in Friday night's Super Rugby clash in Christchurch.

The Crusaders ran in four tries in the opening half hour, and made the most of a 70th-minute yellow card to Force flanker Isi Naisarani to secure the bonus-point win and extend their winning streak to five matches.

The Force fought on bravely after the early onslaught and took control of play early in the second half.

But their inability to make the most of a 59th-minute yellow card to Crusaders substitute Tim Perry ended up costing them dearly, with the home side soon regaining the momentum to cruise to victory.

Adding to the Force's woes were two injuries.

Flanker Kane Koteka was forced off in the first half after copping a brutal hit from rampaging Crusaders No.8 Jordan Taufua while attempting to make a tackle.

And prop Jermaine Ainsley suffered what appeared to be a serious arm injury when a scrum collapsed on top of him.

Ainsley was screaming in pain and writhing on the ground for around a minute before being helped off the field.

The Force had to defend grimly in the opening half as the Crusaders unleashed wave after wave of attack.

By the 30-minute mark, the Crusaders had already scored four tries, with the Force making more than 60 tackles in that period.

Although the Crusaders dominated much of the first half, the Force enjoyed some good moments.

Winger Alex Newsome scored a 60m try in the 18th minute when he picked off a pass from Crusaders lock Matt Todd and sprinted to the line.

And just moments after the halftime buzzer, Force winger Chance Peni twisted and turned his way in a tackle to ground the ball on the line.

Even with Peni's try, the Force still trailed 28-17 at half-time, but it gave them a slither of hope of pulling off an upset.

However, they made mistakes at crucial times in the second half, handing back any momentum to the Crusaders.