The New Zealand Rugby Union has refused permission for the Chiefs to recruit an overseas player to alleviate a backline injury crisis as they defend their Super Rugby title.

The Chiefs sought permission after injuries sidelined centres Andrew Horrell, Tim Nanai-Williams and All Black Richard Kahui.

Horrell may miss the rest of the season with an ankle injury, Nanai-Williams was discharged from hospital last week after treatment for a stomach ulcer, and Kahui has a career-threatening shoulder injury.

The Chiefs’ shortage of fit backs became more serious when fullback Gareth Anscombe broke a toe.

Coach Dave Rennie says the Chiefs asked permission to call in an overseas player but were refused “because there are apparently some rules around time frames.”