Harry McKay is out of contract at season's end and the Blues should be desperate to get the key forward's signature on paper.

McKay is second in the Coleman Medal and has already equalled his career-high goal tally of 22 majors for a season in just seven games in 2021, coming off a massive four-goal against the Bombers on Sunday.

The Blues also have co-captain Patrick Cripps out of contract at the end of 2021 but McKay is arguably becoming the more valuable of the two signatures.

SEN's Sam Edmund has said that it isn't a matter of if but when McKay re-signs with the Blues.

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Edmund also reported that the length of the deal is the current sticking point and said the Blues' form over the next month will be crucial to the period of time McKay commits to Ikon Park.

“Harry McKay is almost the more pressing of the two (contract discussions Carlton has to work through) in that official negotiations haven’t started yet and they’re due to sometime in the next month,” he said on SEN radio.

“This could be result dependant and shape the contract, not in terms of if he’ll sign or not but what I believe is to be what the length of the term will look like.

“If Carlton has a productive next four or five weeks, that will shape the Harry McKay contract and there’s rivals queuing up out the door based on what they’ve seen from him this year.

“If they have a really miserable next four or five weeks, I don’t think the contract will be as long as it might have been.

The Blues had been some pressure following losses to Port Adelaide and Brisbane but after bouncing back against Essendon sit 12th on the ladder.

McKay has been a stand-out for the Blues this season with a career-best game coming against Fremantle in Round 3 where he booted 7.5 with 10 marks.

Edmund went on to say it wasn't unusual for players to take form into account when discussing the length of a new deal.

“Players look at form all the time, they want to see something tangible and they’re no different from the supporter base. They want to see something they can hold on to and commit to.”

What is all the more impressive is that Carlton coach David Teague revealed McKay went into the game feeling unwell.

The Blues face the Western Bulldogs next weekend at Marvel Stadium, who the Blues have a good recent record against, having beat them in two of the duo's last three battles.