WELLINGTON, May 15 (Reuters) - Code-crossing back Sonny Bill Williams has been forced out of a Super Rugby showdown with New Zealand's form centre pairing of Conrad Smith and Ma'a Nonu with a back complaint, the Waikato Chiefs said on Friday.
Williams had been named in the Chiefs lineup to take on the table-topping Wellington Hurricanes in the New Zealand capital on Saturday in what was seen as an audition for an All Black starting berth but the 29-year-old suffered a late strain.
The Chiefs, second in the New Zealand conference with eight wins from 11 games, said the injury was expected to keep out the 2011 World Cup-winner for only a week.
Smith and Nonu have been in supreme form this season as the Hurricanes have racked up 10 wins from 11 matches to prove their worth ahead of the World Cup title defence in England in September.
The duo, who will play their 50th match for the Hurricanes as a midfield pair on Saturday, were the first choice partnership as New Zealand won the Webb Ellis Cup on home soil four years ago, with Williams regularly restricted to either being a reserve or on the wing.
The powerful Williams returned to the Chiefs and union this season after two years at the Sydney Roosters in Australia's rugby league tournament with an eye on another World Cup title bid. (Writing by Patrick Johnston in Singapore; Editing by John O'Brien)