The tie was level at 1-1 after Friday's two singles matches and the crucial doubles encounter on Saturday pitted Belgian's Rubens Bemelmans and Arthur de Greef against Australian's John Peers and Jordan Thompson.
Many expected a tight match between the two teams but the men from Down Under produced a brilliant performance as they wrapped up victory in three sets, winning 6-3 6-4 6-0 on clay in Brussels.
The Aussies have now moved 2-1 ahead, meaning they require just one win from Sunday's two singles matches, and so Belgium have it all to do if they are going to keep their hopes of a maiden Davis Cup title alive.
Van Herck, who represented his country nine times in the Davis Cup during his career, remains in bullish mood ahead of the final day and insists his players will give everything they have to send the crowd home happy.
"They are ready to face the challenge," he said of his team. "We have a lot of confidence to take from yesterday. David will only get better with the confidence from yesterday's match. Steve… we know what he can do. We've come back from 2-1 down before, when everybody was doubting us.
"It's going to be a tough day at the office but it would have been even if we were ahead. We will be ready tomorrow. We will fight and at the end of the day we will see where we go."
Unless there are any late changes on Sunday, Nick Kyrgios will take on David Goffin in the first singles match before Steve Darcis goes up against John Millman if a decider is needed.