WESTERN Bulldogs coach Rodney Eade has slammed the penalty that comes with interchange infringements after it threatened to cause a two-goal turnaround in his side's semi-final win over the Sydney Swans.

The Bulldogs were leading by five points at the 10-minute mark of the second term with Shaun Higgins lining up for goal.

However the umpire signalled an interchange error, with Tim Callan running onto the field without passing through the marked gate after Scott Welsh had come off.

The ball was then handed to Swans defender Tadhg Kennelly, who had his own shot after a 50m penalty from the centre of the ground but hit the post.

"It's a ridiculous penalty," said Eade, who reacted strongly from the coach's box.

"We were having a shot at goal. Fortunately, [Kennelly] hit the post, or it could have been a two-goal turnaround."

The game had been played at breakneck pace to that stage, and the two clubs were locked in a contest that had seven points as its biggest margin.

Eade said it was pleasing to see his players not get caught up in a moment that could have swung the game.

"There was nothing going right for us [at that time], was there? I didn't think it went right for us for most of the game," he said.

"Things conspired against us and I thought the guys, to be in front at half time with that happening, and then even after half time I thought they showed a fair bit of spirit to hang in there and not to get disheartened by it.

"It was a real test for them."