Referee O'Brien suffering

Paddy O'Brien

An achilles tendon injury could spell a premature end to Paddy O'Brien's refereeing career and rob him of a Lions swansong.

O'Brien announced last month he would retire from international rugby this year after a New Zealand-record 37 tests. He had hoped to keep whistling through the Super 12 before finishing with one of the provincial games involving the Lions in June and July.

Instead, O'Brien will sit out the rest of the Super 12 and now rates himself only a "50-50 chance" of recovering in time for the Lions tour.