Chiefs star Sonny Bill Williams has been issued with an official warning from the SANZAR citing commissioner for his crunching tackle on All Blacks teammate Conrad Smith in his side’s Super Rugby loss on Saturday night to the Hurricanes.

Williams flattened the Hurricanes’ captain in the 40th minute of the match in New Plymouth, won 21-13 by the competition’s runaway leaders.

The former NRL star’s shoulder appeared to make contact with Smith’s head but, in Williams’ defence, he used his arms in the tackle and there seemed to be no hint of a shoulder charge.

A warning may be issued by the commissioner for foul play incidents that are very close to, but in his opinion, do not meet the red-card threshold for citings.

On further review of the match footage, the commissioner deemed a warning was appropriate.

The Chiefs will be relieved ahead of their must-win qualifying final on Saturday against the Highlanders in Dunedin.