Mitchell was virtually unsighted in the first half at Accor Stadium on Friday, running for 34 metres from his four carries, but he clicked into gear as the game wore on.

His teammates had struggled to pierce the resolute Melbourne goal-line defence but the fullback found an overlap on the hour mark and sent Campbell Graham across to put the Rabbitohs within eight points.

Mitchell came close to scoring a try of his own but had his run halted inside the 10m zone, before the Storm held on for an 18-10 win.

It was a similar story in round two when the Rabbitohs came within striking distance of a comeback victory against Penrith thanks to some late Mitchell magic.

Demetriou admitted Mitchell would ideally start marshalling the troops earlier on but said it was Souths' defence that cost them against Melbourne.

"I thought the back end of the first half he started getting himself in the game a bit more," he said.

"I thought across the board we were off the pace a little bit.

"(Mitchell) probably needs to find his way into the game a bit earlier but it's not about our attack. It's about our defence."

The Rabbitohs' slow defensive line speed allowed the Storm to roll 71 metres upfield in the set before their first try. Souths then conceded back-to-back penalties and invited Melbourne to bag a second before the half.

The third and final try came on the back of two quick line breaks down the Storm's left side only minutes after halftime.

"Their three tries all came from long distance where we turned the ball over," Demetriou said.

"There are just periods where we're switching off. We're making life hard for ourselves."

Five of the Rabbitohs' middle forwards missed the Storm game through injury but captain Cameron Murray said that did not account for the side's lapses in intensity.

"We've got good depth here at the club," he said.

"We always speak about next-man-up mentality and having confidence in everyone in our top 30.

"I just thought we didn't really turn up today."

Australian Associated Press