NSW Waratahs centre Ben Jacobs has been ruled out for the remainder of the Super 14 season after being diagnosed with a knee ligament rupture from Saturday's victory over the Blues.

Jacobs will undergo surgery to repair his anterior cruciate ligament on Thursday.

It's a big blow to the Waratahs' semi-finals hopes ahead of this week's key clash with the Western Force as Jacobs has started every match for NSW this season at outside centre.

It'll be the first time he has been out of the 22-man match day squad since Round 14 in 2006.

After injuring his left knee against the Crusaders two weeks ago, Jacobs was cleared to play against the Cheetahs and Blues, however it is his right knee which has caused the season-ending injury.

"It's really bad luck for BJ because he's made the No.13 jersey his own over the last couple of years," said coach Ewen McKenzie.

"He's a hugely underrated player and a good organiser in our backline so he's going to be missed.

"For our midfield it's also another hit in terms of experience, however we haven't been afraid to go with youth."

However McKenzie is confident the Waratahs can overcome Jacobs' absence when they take on the Force at Subiaco Oval on Saturday.

"We've got a number of options open to us, and with the way the backline plays it's not like we'll be lining up with guys who aren't used to playing together," McKenzie said.

McKenzie will announce his squad to travel to Perth on Tuesday.

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