ESSENDON coach Matthew Knights has called for the introduction of a fourth umpire in the wake of the Steven Baker-Steve Johnson clashes from last Friday night's St Kilda v Geelong match.

Baker was charged with four offences that drew a 12-week suspension thanks to an existing poor record, while Johnson was charged twice and could face four weeks.

Knights, whose celebrated career at Richmond was regularly punctuated by a running battle with Western Bulldogs tagger Tony Liberatore, says another set of eyes to patrol stoppages would be a good thing.

However, he admitted that illegal behaviour would be almost impossible to stop.

"It may not prevent it because it's player choice at the end of the day with their actions and behaviours," he said at Windy Hill on Tuesday morning.

"But I think an extra pair of eyes particularly around the stoppages - an extra pair of eyes around a congestion of 18 to 20 players ... that would be a preferred option from my perspective".

Knights, who joked that Baker had probably overtaken the often charged and suspended Bombers veteran Dustin Fletcher as the number one villain at the tribunal, said he was sure that if the umpires had seen any of the events on the night they would have paid a free kick in order to settle things down.

"I think a fourth umpire to look at congestion of 20 men around the ball is important for the modern game ... particularly around those scrimmage areas. It then may also allow the umpires that are in their zones, in their 50s, to keep an eye on their zone.

"So it allows the central umpire to control the game, the secondary around the stoppages to watch the stoppages, and then the third and fourth umpires to look in the 50m zones.

"I think that makes sense to me."

Knights did defend the role of taggers, saying not all players assigned a stopping job broke the rules.

"There's different types of taggers, and we get defenders playing on forwards every week, so we've got to be very careful to [not] put taggers into a box of being the villains.

"Not everyone can be the stars, not everyone can take the high marks - there's a role for different people, different people, different body shapes and sizes in our great game.

"As long as they're living within the rules and they're legal … you can still be legal and still have a very physical game of AFL football".