Sydney veteran Dan Hannebery has admitted to making a "stupid error" after he incorrectly manned the mark for Jarryd Roughead's match-winning goal on Friday night.

With just over one minute remaining in the contest and with the scores tied, Roughead marked a kick from Ty Vickery on the 50m arc, and went back to take his kick.

Swans defender Dane Rampe was initially on the mark after Roughead took the grab, but switched with Hannebery before the attempt on goal.

Hannebery was unsure of where the mark was and instead stood two or three metres short of where the mark was taken, which allowed for Roughead to kick the ball from the 50m line, and a metre not beyond it.

“I was really disappointed I didn’t man the mark about two or three metres (forward) as I should’ve,” Hannebery told AFL Today on Fox Sports News on Saturday.

“I replaced Dane Rampe on Roughead and didn’t clarify with either him or the umpire where the mark was, so that’s a clear error of judgment from my point of view.

“I’m extremely disappointed I didn’t clarify that — another stupid error that like a couple of things that quarter, shouldn’t have happened, and it was really disappointing.”

Despite Roughead's kick clearing the goal by a few metres, it's little instances like this one that could be the difference between a win and a loss on another day.

Former North Melbourne and St Kilda midfielder Nick Dal Santo joined Neroli Meadows on AFL Today shortly after Hannebery did, and said Sydney should have placed a taller player on the mark.

“I actually felt a little bit sorry for him listening to those comments. Brutally honest from him,” he said.

“I love that he put his hand up ... I think if he had his time again he would’ve got a taller player on the mark.

“We’re speaking about something so minor but as we saw last night, it can be the difference. He replaced Rampe on the mark which I thought was a great decision, let him go back and be an extra defender or the third up on the line.

“Dan’s not the smallest guy but he’s not the biggest. It’s just these little things in games are costing teams or winning them games.”