The Waratahs got out of jail with a second-half fightback to secure a desperate 32-25 Super Rugby win over the Melbourne Rebels.

After trailing by 19 points at halftime on Friday, the Waratahs scored in the 80th minute through centre David Horwitz to take the much-needed victory.

The Rebels were in a commanding position to claim their first victory of the season and consign the Waratahs to their fourth successive loss but led by five-eighth Bernard Foley, the visitors stood up in the second half at AAMI Park.

Melbourne had a barn-storming first half to take a 25-6 halftime lead but after losing three players - hooker James Hanson and locks Dom Day and Culum Retallick - to concussion, were out on their feet in the second half.

Their error and penalty count also started to mount, proving costly at the death.

It was their second heart-breaking loss after being overrun by the Chiefs last round.

The Waratahs started to find some rhythm after the break and 21-year-old lock Ned Hanigan scored to put his side back in the hunt.

The margin was reduced to seven points when Reece Robinson showed up fellow league convert Marika Koroibete to score in the corner.

With all the rugby being played in the Rebels half the Waratahs reaped the rewards in the 77th minute when they elected to take a scrum 10 metres out rather than a penalty with Michael Wells collecting the five-pointer.

And they weren't done yet, with Horwitz inflicting the mortal blow for the home side.

The Rebels' Reece Hodge was impressive, scoring two tries for a 20-point first-half tally, while Melbourne's hungry backrow of Colby Faing'a, Jordy Reid and Japanese international Amanaki Mafi gave Waratahs skipper Michael Hooper and his troops nightmares at the breakdown.