However, Mathieu Flamini put the ball into his own net in the 90th minute to secure Swansea a valuable point in their fight for survival.
"To get a point against a team challenging for the title is pleasing," Williams told the club's official website. "There is an element of disappointment because we led for so long, but on the whole it's a good point.
"When you're walking off the pitch you're thinking was it a point gained or two dropped, but when we reflect on the game it's a point that takes us to the 30 landmark."
Tuesday's draw has seen the Welsh side move five points clear of the relegation zone with seven games left to play.