Now he's part of North Queensland's Cinderella run that's just one win away from a grand final.

The Cowboys are starting to convince the doubters ahead of their do-or-die clash against the Sydney Roosters at Allianz Stadium on Saturday.

Fensom only made the move to Townsville day's before the NRL season started after salary cap pressures forced him out of the club where he'd won two Mal Meninga Medals as their player of the year.

He was unable to break into the Green Machine that stormed to the prelim before Melbourne knocked them out in a nail-biter.

Now his pre-season move has given him the chance to go one better than his former teammates after he was named on the Cowboys bench to face the Roosters.

"I did a pre-season down there in Canberra and the way things were I had to move on," Fensom said.

"When the Cowboys said they were keen I jumped at the chance. I knew what kind of squad they had up here and what football they were capable of and I was so excited to come up here."

Injuries to key players like Johnathan Thurston and Matt Scott had many doubting they'd even make the finals, but the whole squad lifted behind Michael Morgan and Jason Taumalolo and charged to the final four.

While they've been repeatedly written off, Fensom said the belief had always been there.

"We knew coming into that first semi-final what we were capable of and we proved a few people wrong so far and hopefully we can keep proving those critics wrong," he said.

"Yes and no [it's driven us]. We've spoken about what we're capable of and we know how good we are and how good we can be and what type of squad we can be.

"We just believe in each other, in what we can do. We'll get out there and keep playing footy and keep playing for each other."

Fensom's not one to worry about what opponents have said and hadn't heard Roosters prop Jared Waerea-Hargreaves' comments around targeting Cowboys big bopper Jason Taumalolo.

It's a battle Fensom was looking forward to - and one he'll be involved in up to ears.

Taumalolo leads the NRL for run metres and averages more than 200m per game.

When it comes to the Roosters declaring they'll target him, Fensom had three simple words, "They can try".

"It is going to be a good battle, but I've been blown away with the way Jason's played this year. Just the amount of work he does, how strong and fit he is, it's just incredible," Fensom said.

"It's a pretty amazing sight to see when you're playing out there alongside him.

"They can try, but he's a quality player so it's going to be a good game and the players around Jase have got to help him out as well. It's not a one-man show so everyone's got to put in and play for each other."

Fensom backed Scott to handle a return from a knee reconstruction in the cauldron of a prelim final.

He knows better than most exactly what Scott's going through having come back from a torn anterior cruciate ligament himself in just six months and 18 days.

If Scott does run out against the Roosters, it will have been six months and 14 days since he did his knee in round two.

Cowboys coach Paul Green named him in his 21, but said earlier in the week he would only play if there was an injury.

"Very confident. He's played for Australia, played for Queensland, played in grand finals before. He's a very, very experienced player and I'm sure if anyone can do it he can," Fensom said.