Lyon argued on Wednesday that a lax approach from AFL umpires this year was contributing to increased on-field congestion, and that he was confused by the way officials were adjudicating the game.

However Thomas, frequently critical of umpiring in recent seasons; defended their performance this year, instead contending it was coaching instruction rather than officialdom which was to blame.

"Rossy says umpiring is contributing to the unappealing look of some games. He neglected to add that coaches are the primary contributors," Thomas tweeted on Thursday morning.

"Risk averse, paranoid, job protecting coaches locking down game for fear of being smashed is primary reason 4 aesthetics change & down-time," he continued.

Lyon is widely regarded as a leading mind in defensive tactics, with his team's ranking in the top five for points conceded over each of the past six completed seasons. He has also though been criticised for promoting a suffocating and unappealing style of football, which while successful, is not in the game's best interests.

Thomas agreed with this sentiment.

"Message to AFL Footy Ops Chief: Leave the game alone. It is rapidly losing its uniqueness & appeal. Have a word to coaches. They r culpable," Thomas tweeted.

"Umpiring IMO is better adjudicated this year because incidental technical crap is being overlooked. Stops faking.

"Stoppages increased 3pg. Ball ups down 3pg. Throw-ins up 6pg. That is 100% game style, strategy, tactics devised by coaches. Wake up media!!"

Lyon replaced Thomas at the conclusion of the 2006 season, after Thomas was sacked despite taking the Saints to three consecutive finals series. After initial struggles, Lyon managed to steer St Kilda into successive grand finals, before defecting to Fremantle at the end of 2012. He took the Dockers to their first ever premiership decider in 2013, however remained unable to claim an elusive first premiership of his coaching career.