Magpies forward Callum Wilson was clear on goal in the 92nd minute but was tripped up by Sanchez before the Newcastle man could shoot on goal.
Sanchez was sent off after a VAR check but the incident happened outside the box and Brighton easily defended the free kick.
The game ended 1-1 and BT Sport expert Rio Ferdinand said Sanchez “did well” to turn Wilson down.
“I haven’t looked back at him,” said Potter, Albion’s boss. âBut instinctively it wasn’t much action on our part. We got into trouble, which probably sums up a bit of where we were in the last 20-30 minutes of the game.
âI think it’s one of those things, it’s an instinct, there’s not much time left. It would have been an instant decision.
“And of course when he gets around Rob I think that’s a goal so he saved us this situation and we have to take the punishment and try to learn from it.”
Sanchez, 23, has struggled to regain his best form lately after an impressive start to his career at Albion. The Spain international looked fragile in the 2-2 at Anfield and was unconvincing in Albion’s goal in the draw with Newcastle, resulting in his red card.
Potter, who replaced former goalie Maty Ryan with Sanchez last season, has insisted he will back his “fantastic” inexperienced scorer.
“It’s the life of a goalkeeper,” said the Albion head coach. “It’s the life of a young goalkeeper that you have to face sometimes in adversity, in difficult times.
âAnd that’s always the way you react. A career isn’t just built on success, it’s built on times like today, times when confidence isn’t as high or fitness isn’t as high. is not as good.
“This is how young players develop and grow and we will support him and have the greatest faith and confidence in him. We love him for what he has done with us, he has been fantastic.
“It’s upsetting for him right now but he’s going to come back stronger.”
Sanchez will miss Albion’s trip to Aston Villa on November 20 and will be available for selection for Leeds United at Amex on November 27.
Jason Steele should be between the sticks for the shock at Villa.
Potter added, âJason played in the Carabao Cup so Jason will be in the goal and Kjell will be backing him. Jason has never let us down, he’s a fantastic guy and he will take the opportunity.
âHis cast is fantastic, makes saves. He knows the guys, works with us every day so no problem with Jason. That’s what he’s here for, waiting for an opportunity and being ready and I know that. he will do it.”