An interchange ruling against Sydney left coach Paul Roos fuming at the end of Sunday's 41-point AFL loss to Collingwood.

Roos was on the boundary late in the final term when officials told the umpires to pay a 50m penalty against the Swans for an incorrect interchange.

The penalty meant an easy goal to Magpies small forward Tarkyn Lockyer.

While the match was out of reach for the Swans, Roos was furious and was still arguing with AFL officials after the final siren.

Asked post-match if he was unhappy with the call, Roos drily replied: "Reasonably - that would be an understatement.

"I thought the guy came off and a guy came on, that's what I saw.

"He (the official) clearly saw it differently and I let him know.

"I don't know whether he mixed up the teams, whether we should have got a free kick - maybe he can't tell black and white from red and white."

Roos is concerned what might happen if there is an incorrect call in a close final.

"That's what I said to the AFL official after the game - it doesn't matter in today's game, but gee ...," he said.

"Our bench was surprised. The feedback we got from Collingwood on the way off was that they didn't see anything wrong with what happened.

"I was standing right there - Nick Smith came off and Heath Grundy went on, obviously his report will say differently.

"He said two players went off and he went on too early, or something."

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