EXCLUSIVE: Blues star Tom De Koning 'mentally shot' amid $1.7m decision says Eddie McGuire

Former Collingwood president Eddie McGuire believes the AFL must consider the impact trade speculation is having on players mentally across a season.

It comes as Carlton ruckman Tom De Koning weighs up a mammoth offer from St Kilda, reportedly worth $1.7m per season.

With each passing week, the 25-year-old seems more likely to depart, but the weight of that decision has seemingly impacted his form.

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De Koning would probably have been on the podium in Carlton's best and fairest race after the first three months of the season, but his form has fallen away considerably in the last three weeks.

In part, it has been due to Carlton coach Michael Voss' decision to play two ruckmen, covering for their lack of key forwards in Harry McKay's absence.

While De Koning has previously earned praise as a hybrid ruckman who can play forward, in reality he has never even kicked 10 goals in a single season before.

And of course, the Blues themselves have looked cooked across those three consecutive losses overall. They are now in all likelihood out of the finals hunt.

However, McGuire believes the mental toll of the looming decision has had an enormous impact on De Koning.

"I hate it, because it's become a media fascination and trade period and all that stuff ... it's affecting the players," McGuire told Nine's Eddie and Jimmy podcast.

"If you're a Carlton supporter and you went to that game against Collingwood last week and you're sitting there and you're going 'is he trying?'. It makes you angrier and angrier.

"If you're sitting there and you even think it, and I don't think for a second Tom De Koning was doing anything other than having a real go he just had a bad night, but I think mentally he is shot.

"It's gotten out of hand. It's another one where the AFL would be thinking it's great, it's dominating headlines, but long term it's no good."

The AFL trade period has exploded in popularity over the last 15 years, becoming one of the key pillars of the footy calendar.

Former Essendon coach James Hird agrees with McGuire, saying the decision absolutely would be affecting De Koning's ability to perform.

Despite playing predominantly forward across the last three weeks, De Koning hasn't kicked a goal.

"I think it's affecting the way he's playing. He's not playing great football. He's definitely a great player and better than he is playing," Hird said.

"I feel like he wants to stay at Carlton, but the money is such that it has put him in two minds and it is affecting his football."

Despite the form slump, De Koning is still averaging career highs for disposals, clearances and hit-outs per game.

He and the Blues face Brisbane on Thursday night.