The coach of UFC identity Alex Volkanovski has broken his silence to reveal why he believes Islam Makhachev was permitted to use a banned IV drip before his title fight against the Aussie last Sunday.

Eugene Bareman refrained from calling Russian Makhachev a cheat, but felt the 31-year-old enjoyed a distinct advantage versus 'The Great' in Perth.

Makhachev won a gripping encounter in UFC 284 to retain his lightweight belt and improve his career record to 24-1.

But post fight accusations of Makhachev illegally using an IV drip to rehydrate after cutting weight has soured his epic victory.

After another of Bareman's fighters -  UFC lightweight Dan Hooker - made his feelings on the result and Makhachev well known on Twitter, the New Zealand-based mentor addressed the festering drama himself.

He revealed that Makhachev may have used a loophole in the rules that would actually allow him to legally use an IV before the fight. 

'We have reliable information to a point,' Bareman told The MMA Hour.

'The information falls short because for several reasons, and one of them is that you can actually take an IV before a fight. It just has to be 100ml of saline every 12 hours, in a 12-hour block.

'So what it has to come down to is whether you believe that people are going to take this saline, 100ml, and then stop [all together].

'And the fact that from that [Russian] team there were two fighters.... the information can't reliably tell us yet which fighter illegally hydrated or whether they went over 100ml.

'But I don't know, no information can tell us without a doubt that someone in their team used an IV badge to rehydrate, which is not illegal if you used 100ml. 

'You've just got to ask yourself if it's only 100ml you've got to use for 12 hours, why would you even bother?'

Bareman has his doubts - but added it would be challenging to prove if any improper use of an IV was used by Makhachev or his training partner Zubaira Tukhugov.

'Either it was Zubaira or whether it was Islam, something's gone on there,' he said.

'It's frustrating because the whole sport should be played on an even playing field.

'Then again, you can't reliably say that Islam cheated.'

Using an IV drip to rehydrate was previously commonplace in combat sports, but was banned in UFC in October of 2015 following a decision by USADA, news.com.au reported.

USADA officials introduced the ban because IV drips can contribute to high amounts of weight-cutting - and can also be used to mask performance enhancing drugs.

UFC fighters face bans of up to two years for using IV drips without a medical reason.