They may be in sight of their third straight NRL grand final, but Melbourne's aura of invincibility has gone according to a man who knows a thing or two about rugby league dominance.

Six-time premiership coach Wayne Bennett reckons teams have caught up with the former NRL bullies after the Storm dramatically booked a preliminary final showdown with Cronulla on Friday night.

By rights, no one should be doubting Melbourne's premiership mettle after Saturday night.

They were down to 12 men late in the second half following Jeff Lima's sin binning for a late hit on Michael Ennis.

Yet they soaked up all an inspired Broncos could throw at them at a deafening Suncorp Stadium before snatching a 16-14 victory with a try 46 seconds from fulltime.

It was the perfect way to silence the doubters after the defending champions looked wobbly following their 18-15 finals loss to the New Zealand Warriors last weekend.

Three straight minor premierships also helps Melbourne's premiership case.

Yet Bennett reckoned Melbourne would not find it "straight forward" as they vie for back-to-back trophies.

He may be good mates with Melbourne coach Craig Bellamy, a former Broncos assistant, but Bennett was brutally honest when asked about the Storm's title hopes.

"It is going to be harder for them to win each week," Bennett said.

"They were very dominant for a couple of seasons there but teams are getting closer to them.

"I am great friends with Craig (Bellamy) and I hope they can pull it off but they will certainly be challenged in the next two weeks - it won't be straight forward."

Bellamy didn't seem too concerned by the assessment.

"I don't want to give them too big a rap, but you are a resilient footy team if you win three minor premierships in a row in this competition," he said.

But Bellamy knew Melbourne had to improve if they were to give themselves any chance of being the first team to snatch consecutive titles since the Broncos in the 1990s.

"The first half was not up to the standard that we would like," he said.

"But we were really good especially when we got down to 12 men. The guys kept hanging in there and defending well.

"But you don't usually end up winning semis by just playing a good 40 minutes so we certainly have to improve.

"The Sharks have been wonderfully consistent this year and they are really finding some momentum - we know how tough it is going to be next week."

Storm halfback Cooper Cronk added: "We will do what needs to be done because we play on Friday night against a team that likes to get down and dirty."

Skipper Cameron Smith - at risk of a two-game suspension for a suspected grapple tackle - thought the loss to the Warriors did them the world of good.

"If we had won last week we probably would have let a few things go that needed addressing in our game," he said.

"But that was brought up last Monday leading into this. If we had won against the Warriors we probably would have struggled next week, thinking everything was alright."

Bellamy was beaming over their comeback win.

His only gripe was the sin-binning of Lima, describing it as "a really tough call".

Asked if Ennis had successfully baited the Storm, Bellamy said: "He has plenty of practice. I imagine he was trying to, he might have got us there - he does every week."

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