The central defender captained the side at Everton, when it looked like we'd secured a fourth-successive win in the Premier League, only to be denied by two goals in injury time.
That disappointing finale has made the players all the more determined to get back to winning ways when we face Swansea at the Lane this Sunday, the first of back-to-back home matches followed by Stoke City on Saturday week, December 22.
"We have to come back strongly because we have a big game at home against Swansea, and they are playing well," said William.
"It's important for us to take the three points and we have a few days at the training ground to be ready."
William described Sunday's performance at Goodison Park as 'almost perfect'.
"After we scored, we were so confident we'd win that game," he said. "Everyone was sure we’d go back to London with the three points, so it was a great shame to go back with zero.
"We defended well and attacked well but they started to push on at the end and the last five minutes were really tough. We fought hard but yes, we made some mistakes, so we have to learn."