Williams has been attacked online by some Millers fans for joining League One rivals Pompey.

Warne told The Sheffield Star: "I don't like the thought of our fans criticising any of our players for leaving.

"The players are here, they get paid to do a job and they give it their best. If they then choose to move on then so be it. You don't have to be 'haters'.

"It's just the way that it is. They're not being offensive to fans personally. He wanted to play in the Championship. You can't blame him for that.

"It probably didn't work out as well as he wanted and he thought that Portsmouth was his best move. I sincerely wish him luck, apart from when he plays us."

Williams spent two years with Rotherham, joining the club from Barnsley in 2017.

He helped the Millers get promoted into the Championship in 2018, but was unable to stop them sliding back into League One.

Warne wanted to keep the Australian winger at the New York Stadium, but Williams decided to depart and sign for Portsmouth.

"I'm disappointed he's gone," the manager said. "I spoke to Ryan many times last season about staying on. He really wanted to kick-start his international career.

"When I spoke to him, he thought he would have an opportunity in the Championship. In fairness, I thought he would as well.

"However, I know how a lot of people tell stories in football ... 'Yeah, you're definitely on our list.' They get the players excited. I knew a couple of Championship clubs who liked him and had spoken to him.

“The player gets his head turned a little bit. That's what's happened."

He added:  "It's that late in the day now that the Championship club he wanted possibly didn't come forward. Then Portsmouth came forward.

"I can't put words into his mouth. This is just what I think."