The Western Force have put a major dent in the Crusaders' Super Rugby Trans-Tasman title hopes, unable to land the killer blow but still denying the heavyweights a bonus point in a 29-21 loss in Christchurch.

After going down 29-14 early in the second half, the Force dominated field position and possession against the formidable Super Rugby Aotearoa champions.

Reduced to 14 men thanks to a late injury to replacement Tim Anstee, the Force finally cracked the line with the final play of the game when captain Kyle Godwin's long-range kick was chased down by Jordan Olowofela.

It caught the Crusaders napping and took away a bonus point that could prove the difference between high-flying New Zealand teams in a tournament that features a stand-alone final.

"It's been a bit of theme, leaking late points and that one really hurts when it's a points race and there's a fight at the top there," Crusaders captain Scott Barrett said.

"We were aware of what the Force bring - niggle and stuff at the breakdown - they certainly challenged us there and stopped a wee bit of our flow."

Earlier Toni Pulu scored a brilliant try in just the second minute, stepping inside and beating three defenders as the Force's pursuit of a first win in Christchurch started well.

But the winger, a smoky for a Wallabies Test cap next month, was helped from the field with an apparent ankle injury just before halftime.

The Crusaders were without rested quartet Richie Mo'unga, Sam Whitelock, Sevu Reece and George Bower at Orangetheory Stadium.

Still, they looked to have wrestled back momentum with two tries in response to Pulu's early effort before Ollie Callan crossed in his starting debut in the No.8 jersey.

Up 29-14, Crusaders fullback Will Jordan was denied a third try, strangely because of a Force error when Jake Strachan stepped on the sideline before he threw a pass that teammate Domingo Miotti knocked on.

It was all the Force for the last 20 minutes, denied a brilliant try when Richard Kahui's tap-on pass was deemed forward while Godwin was also held up over the line.

That was as close as they got until the final minute, the Force now boasting three losses by 10 points or less from their four Trans-Tasman clashes so far.

"We've been growing as a team every week," Godwin said.

"I'm really proud of the guys (even though) we couldn't go all the way and probably left a few tries out there while in the attacking zone.

"We've got a lot of potential ... the Crusaders are a world-class side and we can stick with them."