Sanchez, looked unconvincing in the first half as he was beaten at the near post after five minutes from Tomas Soucek's header.
Sanchez was caught in the wrong position as the West Ham' s Czech international glanced home a header from a dangerous in-swinging corner.
The Brighton goalkeeper also looked uncomfortable with the ball at his feet and needless gave the ball away twice to West Ham's attackers.
The Spain international also had a VAR let off in second half when he once again flapped at a corner and the ball deflected into the net but was ruled out for offside.
Sanchez did however regroup and produced two fine saves in the dying moments to help Albion gain a point from Neal Maupay's late leveller.
It's been a tough period for Sanchez who was struggling for his best form before he received a red card in the 1-1 draw against Newcastle.
"He made a couple of saves towards the end," said Potter. "But he didn't have the best of first halves by his standards so it was nice for him to come through that and help us in the second half. Then he was really good.
"He is a young goalkeeper. Sometimes you have to go through this process but we are happy with Rob. It was nice he contributed to the team in getting the point. The West Ham goal keeper did the same."
Potter will be without Jeremy Sarmiento (hamstring), Adam Lallana (thigh) and Adam Webster (calf) at Southampton as all three were injured at West Ham.
"There’s no good news, but there’s no bad news either as it’s still early days in terms of assessing," said Potter.
"There’s nothing to really report, but Adam Lallana, Jeremy Sarmiento and Adam Webster won’t be available for the weekend.
"The extent of the injuries though, I haven’t got any information on that yet."