Richmond coach Damien Hardwick said coughing up a five-goal lead was of greater concern than the decision to not pay Dion Prestia a 50m penalty after the siren.

Prestia would have had the opportunity to tie the game, but the umpires' collective call was Chad Warner had not heard the whistle for a free kick when he booted the ball into the crowd on the final siren in Sydney's six-point win.

Hardwick said he wasn't sure how the decision should have been adjudicated.

"It's irrelevant. You can look at that last incident, but the fact of the matter is we were up by 30 (33) points, it's easy to look at the last game, but we should have iced the game," Hardwick said.

"Seventy-five per cent of the time I thought we were pretty good, 25 per cent lapse – especially in the third quarter – there were some things we thought we could have done a bit better.

"Everyone will always look at the last play and the what-ifs, but the fact of the matter is, if you're 33 points up, you shouldn't lose."

Hardwick bemoaned Richmond's ill-discipline in the closely fought match.

"Mills, their seventh, probably generated a little bit of income for them, and we probably didn't use the ball as well as we would have liked in that situation. And that's on us as coaches to prepare the players a little bit better in that situation," Hardwick said.

"Last quarter, we rectified it and had our chances, and we kicked 2.6 or something like that (3.6) to their six straight. There's the game.

"It would be remiss of me to say we'll give up five free-kick goals again, two from 50m penalties and a few downfield. We just kill ourselves at various stages and we expect better. It's disappointing to lose a game like this through ill-discipline."