A CONTENTIOUS free kick paid against Richmond's Reece Conca for holding the ball in the last quarter of their 10-point loss to the Western Bulldogs was the correct decision, umpires coach Hayden Kennedy says.

Conca was tackled immediately after taking possession following a ball-up outside the Bulldogs' forward 50, with 12 and a half minutes remaining in the fourth quarter.

Richmond was one point up at the time, and the subsequent free kick and 50m penalty for not handing the ball back in a timely manner, resulted in a goal to Marcus Bontempelli and the Bulldogs taking the lead in a close match.

Kennedy, speaking on Whistleblowers, said he and the umpire coaches were comfortable with the decision.

"What Jordan [Bannister] does, he allows Reece some time in which to show a genuine attempt to dispose of the ball, or make an attempt to dispose," Kennedy said.

"Jordan doesn't see that, he allows enough time, so therefore he pays holding the ball, [no] genuine attempt." 

The 50m penalty paid was also given the all-clear by Kennedy.

Hawk Cyril Rioli almost took a contender for mark of the year over Port Adelaide's Matthew Broadbent, but the mark was not paid when he failed to control the ball while falling to the ground. 

While commentators were calling for the mark to be paid in respect to the "theatre" of the game, Kennedy said umpires judged each mark on its merits. 

"It's not a mark – it's a great attempt, and it would have been fantastic for Cyril to control that one, but as you can see, as the ball comes down, there's a grab there and it comes out," he said.

"Unfortunately from an umpiring perspective, it wasn't controlled, and we had one umpire there who saw that and was courageous enough to, despite the theatre and despite the great leap, award it correctly as a ball-up." 

Four field umpires were trialled over the bye rounds, and Kennedy said it was a mixed success.

"We'll be presenting the information to the executive and to the Commission, and when the time is right," he said.

"Some of the stats that came out – our decision-making didn't really improve with the four umpys, GPS results show we ran one and a half kays less, so just under 13km, and less at a high intensity."

Kennedy admitted the current number of umpires (32) may not be enough to support four per game, but said it was a good opportunity for others around the country to stand up.

"I think the three-umpire system that we've got at the moment is really good at the majority of games, but certainly, if you look at Thursday night, Friday night's game, where it's really hard, tough contested footy over a long period of time, over two hours, maybe the extra support of another umpire can benefit performance," he said.