Spurs were comfortable 3-0 winners on Saturday via goals from Pape Matar Sarr, Lucas Bergvall and Micky van de Ven. Tomas Soucek also saw red for West Ham.
Potter said afterwards: "I’m disappointed of course with the end result in the second half because we made one mistake.
"We had defended the set-pieces well and we made a mistake for the first goal.
"Obviously the red card quickly in the space of five minutes changes the dynamic because they get another goal and then we're on the back foot.
"For the first half, I thought it was a decent performance. There were lots of positives in the first half and that's the painful thing because the scoreline in the end is completely unpleasant for us.
"But at the same time there were glimpses of positivity, I thought, especially in the first half. Like I said, the second half, the game goes away from us so quickly and that's the level and we have to learn from that. Like I said, the first half is what we have to focus on and remain positive.
"I thought the front four were dangerous in the first half."
Spurs didn't create so much
Potter also said, "I thought they were supported well with Kyle Walker-Peters on the right, and supported well with Malik Diouf on the left.
"I don't think Tottenham's chances against us created too much at all. They had pressure and set-pieces which is what we had to deal with and again I thought we dealt with them well until the start of the second half when we made a mistake.
"And that's again the level, the detail, the margins and then we went 1-0 behind and quickly went down to ten men.
"The game changed at that point and then it's an uncomfortable second half for us, there's no doubt.
"At the moment we're just hurting because we've lost the game, I understand that completely.
"We've played two games at home against the World Club champions and another team that's also in the Champions League, so there's quality against us. Nevertheless, we're disappointed because we wanted to do better, we wanted to have more points."