Melbourne tagger James Harmes has conquered the game's best in recent weeks.

But as the club looks forward to its first final in 12 years, the improving Demon is refocusing his attentions back to where it all began – in a crucial run-with role against Joel Selwood.

Harmes had never played a full game as a tagger prior to being handed the key job on the Geelong captain ahead of his side's round 18 clash with the Cats.

Used fleetingly and sporadically in the position before, it was the first time Harmes had been asked to put all of his effort into stopping the opposition's best player for an entire match.

He relished the role, producing arguably the best performance of his career to date against Selwood and growing into a full-time tagger in the month since that important display.

Now, he's ready to face the Cats skipper once again – even if his coach Simon Goodwin is still keeping his cards close to his chest.

"I'm not too sure who I'll be on, we'll see what happens," Harmes told AFL.com.au.

"'Goody' normally comes up to me later in the week and lets me know. I'd say either Joel Selwood or Patrick Dangerfield, but I haven't been told yet."

While Harmes is adamant he has not yet been informed who he will be standing alongside at the first bounce on Friday night, he has an inkling it's going to be Selwood.

The last time they met, when the Cats got over the line thanks to a Zach Tuohy kick after the siren in July, Selwood was limited to just 16 disposals and four clearances.

It was the Geelong captain's lowest output of the season, and it provided Harmes with plenty of confidence going forward.

"He works really hard, he's pretty strong and he's a real competitor," Harmes said.

"He's definitely one that I'll have to watch around the stoppages. You can easily lose him in there."

While Harmes' job on Selwood won plenty of plaudits, it was actually the game prior against the Western Bulldogs when Goodwin first approached the 22-year-old about being used as a tagger.