Cronulla Sharks fullback William Kennedy is facing an extended stint on the sidelines after suffering an ankle injury, and will be racing the clock to return for the NRL finals.

The Sharks confirmed on Monday morning that he is undergoing surgery on the ankle today, and will miss between five and six weeks.

Kennedy showed no ill-effects of the injury during a thrilling golden point victory over the South Sydney Rabbitohs on Saturday evening, however, is understood to have played through the pain barrier in completing the match, which went to its 88th minute.

In a medical update, the Sharks confirmed that it was only after scans were returned that they were able to ascertain the pain Kennedy experienced in his ankle was in fact an injury requiring surgery to correct the issue.

The Sharks are holding out hope that Kennedy may be able to return for the final round of the regular season when Cronulla play the Newcastle Knights, however, with only five rounds remaining, it would appear more likely that Kennedy's return date will be the opening week of the NRL finals - the same date the Penrith Panthers will welcome back Nathan Cleary from suspension, and are hopeful of having Jarome Luai back on the park from injury.

Cronulla confirmed they sustained no other injuries from South Sydney's clash and with the exception of Kennedy, Jack Williams and Sione Katoa, who are both out for the season, will be at full strength for next week's game against the St George Illawarra Dragons.

The Sharks are likely to replace Kennedy with Lachlan Miller, who made his debut earlier this year having transitioned from rugby sevens.