We looked in control when Darren Bent headed home from Steed Malbranque's cross after 26 minutes but, having looked dangerous early on, Newcastle found an equaliser via Nicky Butt's low drive seconds before the interval.
Newcastle came out firing and had been denied by the woodwork by the time Geremi made it 2-1 via a free-kick.
Robinson then saved superbly on two occasions before Michael Owen added the third and it looked already over when Obafemi Martins slotted the fourth with 10 minutes left.
"It’s quite strange because we had a good first half, the team was fine but without any apparent reason the direction of the match changed," reflected Juande.
"I think it was due to a lack of tension and the fact that the points weren’t very important. Newcastle played more than us and the points were more important for them."
Asked why he went for a 4-3-3 system, Juande replied: "We’re in a phase of the season that’s not so important so it’s useful to see the players in a different way of playing and we’re looking to use the squad. That will then help us make the correct decisions for next season."
Meanwhile, Juande reported that Jermaine Jenas was missing through illness.
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Juande Ramos was left perplexed as Sunday's match turned around in Newcastle's favour 'without any apparent reason'.