The Melbourne Storm are now facing the harsh reality of heading into Saturday night's preliminary final with their leading try scorer.

Winger Marika Koroibete battled through a 10-minute running session on Wednesday afternoon before limping off the track as main training began.

It was the Fijian's first attempt at running since suffering a lacerated Achilles a fortnight ago against the Roosters.

Draw Widget - Finals Week 3 - Storm vs Cowboys

Koroibete has been a revelation this season for Melbourne, scoring a team-high 16 tries from 22 games this season.

However his condition will need to significantly improve in just three days before the Cowboys come to AAMI Park to fight for a place in next week's decider.

"He has really improved a lot in the last 24 hours, we were all a bit doomy and gloomy on Monday to be quite honest," Storm coach Craig Bellamy said.

"We haven't really made a decision there yet, I don't want to have to make a decision if we don't need to.

"We will just see how Marika goes today and if it doesn't look so good we will probably make a decision from there."

As Koroibete hobbled off the training track, Young Tonumaipea stood in his place out on the wing as the Storm fine-tuned their attack.

Tonumaipea has spent majority of the year in reserve grade after playing the first four games of the season but appears ready in waiting should the Storm match committee look to spring a surprise.

While Koroibete's omission could be on the cards, North Queensland five-eighth Michael Morgan is the big inclusion compared to the last time the Storm and the Cowboys crossed paths three weeks ago.

That night North Queensland leaned heavily on Johnathan Thurston, culminating in the 14-6 defeat which put an end to their minor premiership aspirations.

This time around Morgan will arrive with his teammates in Melbourne on the back of a dominant display against the Sharks that saw him notch three line breaks, two tries and an assist.

"He is definitely a very dangerous ball runner and he has obviously improved his skills as well since he's been playing five-eighth," Bellamy said.

"He's strong and he's quick, he certainly adds another dimension to them that we didn't have to face last time."