Williams said "He was tight, and I think because the surface can give way a little bit, of course, it's natural at this time of year, and with the rain that we had, it's actually all things considered the pitch is very good.
"But it's impossible for the amount of volume of rain it has had and games that have been played, so when you slip a lot you can start to put extra effort in, but he felt a tightness in his hamstring.
He was able to start the second half and then we could get him off so hopefully, we have stopped it from being a little more serious."