Cronulla halfback Michael Sullivan revealed he had drawn inspiration from his dying mother in cementing a first grade spot this year.

LeeAnne Sullivan has terminal cancer of the bone and would've been proud of her son as he engineered a 25-16 upset victory over St George Illawarra in the National Rugby League clash at Toyota Park.

The No.7 scored a try, set up three others and booted a field goal to leave the Dragons walking on a tightrope to make the finals.

"She's one of my biggest fans, as all mums are, and in the off-season when things got tough she was my inspiration," said Sullivan.

"I made a goal to myself to make sure I made the grade this year just for her. And she lives off it. She loves it and she's down every week.

"They gave her six months (to live) probably 12 months ago and said 'enjoy your last Christmas' but she's been battling on.

"She's been really positive and she provides a lot of strength for our family."

Sullivan is re-negotiating a new deal with the club and the performance will certainly make coach Chris Anderson sit up and take notice.

The 23-year-old has been playing five-eighth this season but Anderson decided to shift him to halfback, axing injured captain Brett Kimmorley's replacement Andrew Dallalana.

Sullivan scored a controversial try in the 43rd minute to break a four-all deadlock, with a hint of a knock-on following a pass by fullback David Peachey.

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