AFL UMPIRES coach Hayden Kennedy has described contact between field umpire Sam Hay and Hawthorn's Luke Breust as an "unfortunate accident".

The incident occurred in the fourth quarter of the Hawks' Saturday night clash with North Melbourne. Hay ran into Breust while the Hawk was coming to his senses after landing on his back in a marking contest with Kangaroo Ben Jacobs.

The umpire's knee made contact with Breust's head, with the duo completely unaware of each other's presence.

"What you'll see is that Sam's looking in a completely different position," Kennedy told AFL.com.au's show Whistleblowers. "It's not often that we see players are down at ground level.

"Once again it was an unfortunate accident."

The Hawks have not been immune to contact with umpires this season. Paul Puopolo sustained a corked thigh when he ran through the banner before his side's 70-point win over the Western Bulldogs in Launceston in round three.

On that occasion, emergency field umpire Jack Edwards, who is yet to debut, bumped into Puopolo while he was completing his run through.

To hear more from Kennedy and former Magpie and Saint Luke Ball reviewing a number of other umpiring decisions, click on the video above.