The Chiefs have suffered a serious setback ahead of Friday's Super 14 rugby semifinal against the Hurricanes, with All Blacks centre Richard Kahui ruled out due to an ongoing calf injury.

Kahui bruised his calf two weeks ago against the Hurricanes and didn't play in last weekend's win over the Brumbies.

Chiefs Coach Ian Foster said it now appears he may have suffered a small tear but he's about 85 percent fit and should be available for the final next week if the Chiefs qualify.

Meanwhile, Jeremy Thrush was forced out of the Hurricanes training earlier today after taking a knock to his elbow.

The injury is being monitored and Bryan Evans will slot in at lock if Thrush is ruled out, with Api Naikatini coming to the bench.

The Chiefs/Hurricanes match kicks off at 7:35pm on Friday and the second semifinal between the Bulls and Crusaders kicks off at 1am on Sunday.