We looked on course for victory when Eric Dier capped what had been a dominant first half display by opening the scoring five minutes before half-time.
We were denied by Rob Elliot in the Newcastle goal on numerous occasions and as what could have been a decisive second goal proved elusive, so the visitors grew into the game.
Newcastle levelled through substitute Aleksander Mitrovic on 74 minutes and then snatched all three points through Ayoze Perez in added time - our first loss in 15 in the Premier League and first since the opening day of the season.
“We feel very disappointed,” said Mauricio. “We played very well in the first half and deserved to score maybe one or two more.
“But you know, in football, when you don’t kill off the game, things can happen.
“In the second half we were in control until they scored.
“The problem is not about energy but if you make mistakes, you can pay and today was unlucky because the second half was under control and if we analyse the game, it’s not fair that we lost.
“But you need to work hard for 90, 95 minutes and it’s never finished until the referee’s whistle.”
Eric Dier told us that the lads would learn from their mistakes and look to bounce back at Southampton on Saturday.
“You always need to learn and this is a good mentality,” added Mauricio. “We need assess why it happened. In football, sometimes it’s difficult to explain.
“I thought the first half was fantastic and it’s difficult to understand why we lost control in the second half.”