Stuart "Trojan" McKinnon, 46, used encrypted BlackBerry phones to sell 20,000 MDMA tablets in March 2017 - completely unaware undercover police were his customers.

The tablets weighed 4.9kg with a purity of 12.5pc.

But the Court of Criminal Appeal on Wednesday quashed his original 11-year jail term after finding the sentencing judge made a legal error when considering two other offences.

As well as pleading guilty to the drug supply, the former manager and head trainer of Sydney's Bulldog Gym admitted possessing four vials of testosterone and $237,700 in cash police found during his arrest in May 2018.

The Muay Thai kickboxer who holds a karate black-belt explained he used testosterone to train and had been holding the cash for his cocaine supplier.

His $80,000 cocaine debt could be paid down in instalments of $2500 each time he warehoused the cash, he said.

The debt was reduced by $5000 for each sale of 10,000 MDMA tablets.

In resentencing, the appeal judges said notes on McKinnon's custody file are "uniformly positive" and describe him as an asset, compliant and someone who conducts himself in "a polite and well-mannered" way, the court said.

He could have moved to a medium-security prison but holds a trusted position in the Metropolitan Special Programs Centre at Long Bay.

"One note praises the applicant for de-escalating issues in the yard, 'stopping anything from getting physical'," Justice Anthony Payne said.

McKinnon boasts 18 knockouts and 27 wins in his 31-fight kickboxing career and an undefeated boxing record, according to Bulldog Gym's website.

He also trained several world-class fighters, including younger brother Steve - a WBC Muay Thai world champion.

Special circumstances were also found due to McKinnon being a first-time prisoner and needing treatment for drug addiction and other health problems.

His new eight-year term now ends in 2026 and he'll be eligible for parole in 2023 not 2025.

Australian Associated Press