The 20-year-old has made just three starts in more than three years with the U's, but Williams believes that Guy can overcome injury problems to prove his worth.
"I would like Jamie to stay and he's in my plans for next season," said Williams.
"There are a lot of things a young man has to weigh up when considering his future.
"He has said to me that he feels he may need to move on, but I disagree with that.
"If a club was to come in with an offer that was acceptable and Jamie wanted to go, then we would have to consider it. That has always been our policy."