The goalless draw with Manchester City was Swansea's seventh Barclays Premier League game without a win. Their last victory came against Newcastle at the start of March, one week after beating Bradford at Wembley. Defender Williams has been frustrated by the sequence of results which have seen Swansea take just three points from a possible 21.
"It's not good enough," he said. "If you take away the Arsenal and the Tottenham games, we should have done a lot better in each of the other matches. I think, for whatever reason, we took our eye off the ball. But I also thought against Manchester City we performed well and were back on our game."
But the Wales captain rejected suggestions there has been any lack of effort from the Swans with silverware and safety secured.
"It's not been enjoyable not winning a game for so many weeks, but a draw against the ex-champions isn't a bad result," he said. "It's easy to say we thought the season was over after Wembley, but I didn't think like that and I don't believe any of the other players did.
"It may look that way from the outside, but we've done well in games. There have just been critical periods when the opposition have scored, while we've missed chances and that has cost us. We put pressure on ourselves, we said the City game was an important match and we wanted to perform well. I think we did that."
Williams, who has been heavily linked with moves to Liverpool and Arsenal, turned in an outstanding individual display against City which is sure to have impressed any potential suitors. And Williams felt his performance was just part of an excellent collective defensive display.
"It's the best we have played in recent weeks," he said.
"The second half was tough, we got tired and I think the front players were working so hard defensively when Manchester City got on the ball it was hard for them to actually keep it from us.
"City were always going to have chances, but the pleasing thing for me at the back was the way we stuck together and helped each other out."
Source: PA
Source: PA