Everton went 2-0 up in the 72nd minute when Sigurdsson put the ball past Arrizabalaga from the rebound after his penalty kick was saved by the Chelsea goalkeeper following a foul in the box on Richarlison by Marcos Alonso.
And, after Marcos Alonso had fouled the Brazil worldwide inside the box on 72 minutes, Sigurdsson secured his side all three points on the second attempt after Kepa Arrizabalaga had saved his initial penalty.
"It would be easier for me just to speak about the second half".
"I told our players at halftime they have to do everything different". What I saw in the second half is what we do every day in training.
Marco Silva believes Everton's first win over a top-six side in more than two years has vindicated his ongoing project at Goodison Park.
They then took full control of the contest.
The result has led to some rather inquisitive articles being written on Monday regarding his future at the helm, with Champions League qualification now looking like a tough ask, and Maurizio Sarri, currently at Chelsea, remains one of the names for next season.
"I can not explain it".
Pickford: "We know we weren't great in the first half and we didn't do what we were expected to, but if you don't play well and it's still 0-0 it's a great stepping stone". It's odd and we stopped to defend and counter-attack. "We have to play eight matches now and we have to fight for our possibilities".