The Melbourne Rebels are set to go into their crunch Super Rugby clash with the Waratahs without three key backs including winger Tom English whose season could be over.

The Rebels were given a wake-up call about their ambitions by title-holders the Highlanders, who romped to a 27-3 win at AAMI Park.

The loss was compounded by injuries to English (knee), veteran centre Tamati Ellison (hamstring) and fullback Jonah Placid (shoulder) which meant the trio were unable to finish the match.

English left the changerooms with his leg in a brace and the initial diagnosis was a grade 2 ACL tear.

Scans will confirm the length of time the 25-year-old will be sidelined however there are fears he could miss six weeks, with the entire season a possibility.

The absence of Ellison for next Sunday’s clash in Sydney would be a big blow, with the Rebels missing his playmaking skills and defensive work when he sat out their round three game through concussion.

With their blockbusting winger Sefa Naivalu still a game or two away from returning from his badly broken leg and utility back Mike Harris unavailable with a quad injury the backline stocks are at an all-time low.

The Rebels have only beaten NSW once in 10 meetings, a two-point win in Melbourne in 2013.

Rebels stand-in captain Sean McMahon said his team’s heavy travel schedule couldn’t be blamed for their error-ridden performance.

He gave credit to the Highlanders’ defensive pressure, with their game plan successfully spoiling the Rebels’ attack at the set piece.

“It all came down to little mistakes that we did and first phase turnovers which gave them opportunities in defence to come in and attack us,” McMahon said

“We’ll work on that but best thing about Super Rugby we’ve always got another week.”