Written off as title pretenders midway through the season, the NSW Waratahs enter Saturday night's Super 14 semi-final just two wins away from completing the greatest revival in the tournament's 13-year history.

No team since the competition began in 1996 can boast of going from 13th to first in a single season.

But that is exactly what the Waratahs are striving for after overcoming a season of off-field turmoil, injuries to several key players and a wretched draw culminating in a draining pre-finals journey to South Africa and back.

Waratahs and Wallabies great Mark Ella is one supporter who would happily eat humble pie if NSW could pull off what appeared rugby's own mission impossible just a few weeks ago.

"It would be unbelievable and I hope they do it," Ella told AAP.

"I see no reason why they couldn't.

"I think they'll beat the Sharks and the way they're playing at the moment, whether it's a Sydney final or in New Zealand, I think the Waratahs have got the ability to do it.

"I guess last year they had a couple of injuries, particularly to (Dan) Vickerman and (Phil) Waugh, which definitely upset their rhythm.

"Their strength is through their forwards and they're absolutely on fire at the moment and their forward strength can take them all the way."

Ella has joined the thousands of former disbelievers who now believe in the Tahs.

One of Australia's finest-ever players, Ella condemned NSW as boring, "way off the pace" and not in the title hunt unless they made some dramatic improvement in the wake of their 34-7 capitulation to the Crusaders in Christchurch in round six.

"We're just playing crazy football, so we're a long way from being one of the powerhouses in rugby at the moment," he said at the time.

Now, though, the Waratahs need only to repeat their round-11 victory over the Sharks at the SFS to progress to Saturday week's championship final against either the Crusaders or Hurricanes.

And if history is against NSW winning the final, it strongly favours the Waratahs from at least making the title match.

Tellingly, in a total of 24 matches, only four away teams have ever won semi-finals - but none in the last six years.

With a perfect six-from-six record in Sydney this campaign, the Waratahs' home-ground advantage appears doubly important.

"We've always had a good record here," noted NSW coach Ewen McKenzie.

"Not last year, but over time we've had a good record here.

"I think we're up around the 80, 85 per cent success mark, so it's been good for us this year and we're hoping that continues."

Still, the Waratahs are wary of the Sharks, who won a bunch of matches on the road to be unbeaten for the first nine rounds this season.

The South Africans say they have adjusted well since arriving from Durban on Monday and are optimistic about springing an upset.

NSW winger Lote Tuqiri said the Waratahs would be foolish to underestimate their opponents, who were boosted by news that superboot Francois Steyn would definitely take his place in the centres after being in doubt all week with a rib injury.

"Francois Steyn can kick from 60, 70 metres, so our discipline has got to be alright on the night," Tuqiri said.

"They have guys like (Ryan) Kankowski at No.8, who can run with the best of them. He's quicker than some of our backs.

"They are strong everywhere."

While Steyn is in, the Waratahs confirmed reserve flanker David Lyons would miss the knockout match with a hamstring injury.

Beau Robinson comes onto the bench.

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