The Melbourne Rebels had two players red-carded but still condemned the New South Wales Waratahs to a winless Super Rugby AU season with a 36-25 victory at Western Sydney Stadium on Saturday.

With both teams out of playoff contention after the Western Force beat the Queensland Reds on Friday, there was only pride on the line in a match between two teams who have badly under-performed this season.

Tries from Stacey Ili, Michael Wells, Rob Leota and Matt Gibbon combined with 16 points from the boot of Matt To'omua proved enough to give the Rebels the win, but it remains to be seen if it is enough to save the job of coach Dave Wessels.

The Waratahs conceded a try after 36 seconds when a To'omua crosskick found Ili on the wing, but they battled their way back into the contest after Rebels number eight Isi Naisarani was shown a red card for a head-high tackle and a couple of punches.

Winger Mark Nawaqanitawase and fullback Jack Maddocks crossed in the 20 minutes the Rebels were short-handed, and the home side were within three points of the lead at 21-18 at the break.

Lock Leota crossed from close range soon after the resumption to extend the lead but the Waratahs struck back through flanker Carlo Tizzano, who forced the ball down under a pile of bodies on the try line.

Prop Gibbon crossed in the 66th minute, however, giving the Rebels enough breathing room to hold on with 13 men when James Hanson was yellow-carded and Pone Fa'amausili saw red in the last five minutes for another dangerous tackle.

The Rebels finished fourth in the standings with three wins from eight matches, while the Waratahs were rock bottom with only three losing bonus points.

The ACT Brumbies and Western Force, who finished second and third, play off next weekend to decide who takes on the Queensland Reds for the Super Rugby AU title in Brisbane on May 8.