Nick Woltemade’s own goal was the difference as Sunderland won the first Premier League Tyne-Wear derby since 2016.
The newly promoted side are now four points ahead of Newcastle in the league table, sitting in seventh with 26 from their 16 games.
Speaking after the game, a clearly furious Guimaraes didn’t hold back when asked about his side’s performance, criticising his teammate’s “mentality.”
He said: "I'm very angry, I'm so embarrassed and I'm so frustrated.
"There was no crossing, no passing and no shooting. No nothing. It was a mess, in my opinion.
"We know we have a better team than them (Sunderland) but we didn't play like the better team. It was a mess.
"The consistency isn't there, the mentality isn't there. We didn't compete. The fans expect and deserve better.
"We accepted the way they play with the long balls. You need to compete in a derby and we didn't."
Guimaraes added it was his most painful defeat as a Newcastle player stating: "Definitely, yes. Not just as a defeat, more the way we play. Disappointed, frustrated, lack of energy, don't put the things that we are able to do, cross the ball, pass the ball.
"We were like a mess in my point of view. Disappointed, angry. This one is a tough one to accept.
"I've played many, many derbies in my career. It's not easy to get a defeat, but today I think we disappointed the fans. We disappointed the fans in general because they were expecting much more. We were as well.
"But we didn't perform like the team that should come here with the right mentality. So yeah, we understand the fans.
"Now we have just, for me, one way to go. That is beating everyone, improve our form, qualify the club for the semi-final of the Carabao Cup, qualify for the Champions League and improve our level in the Premier League as well. And just a final one for me, Bruno."