Aaron Cruden is set to undergo scans on his injured knee on Monday, but his club coach Dave Rennie was bracing for the worst.
The All Blacks fly-half's participation at the Rugby World Cup is in doubt, after he was injured in a Super Rugby fixture on Friday.
Cruden's Chiefs were 26-9 winners over the Crusaders despite losing the 26-year-old in the 19th minute in Christchurch.
"Aaron was just running and his knee caved in. It was a sideways movement," Rennie said on Monday.
Cruden injured the same knee - his right - at the World Cup in 2011, when he hyperextended the joint.