Newcastle sporting director Dan Ashworth admitted the club were shocked to discover midfielder Sandro Tonali had bet on matches during his time with AC Milan that led to a 10-month ban from football.

Tonali cost the Magpies a reported £60 million ($76 million) in July to become the most expensive Italian player of all time.

However, he played just 12 times for the Premier League club before being banned as part of an investigation by Italian prosecutors into gambling on football.

The 23-year-old placed multiple bets including on matches involving Milan during his time with the Italian giants.

His agent has said Tonali has a gambling addiction.

The English Football Association are also reportedly investigating whether Tonali broke betting rules after joining Newcastle.

Players are not permitted to gamble on any football matches, whether they are involved or not.

"It was a massive shock, a massive surprise. Dealing with it was new to all of us. It came from nowhere," Ashworth told reporters on Friday.

"He was a big signing for us. We didn't expect it. You look at yourself. Could I have done better? Could we have known? Should we have known? You look at your processes.

"I have been doing this for 16 years and it has never happened before."

Ashworth refused to be drawn on whether Milan knew of Tonali's gambling prior to the transfer and the possibility of legal action if they did.

"It's really difficult for me to get into what other clubs do or don't know," he added.

"All we can do is look at our own internal investigation and internal process. It's a really difficult question for me to answer - I just don't know.

Ashworth said Tonali had been a "top-class individual and professional" since news of his betting broke.

But he refused to deny that the player's salary may be cut during his ban.

Mental test

Newcastle are 80 percent owned by the Saudi sovereign wealth fund and could look to the Gulf for a replacement in the January transfer window.

The Saudi Pro League has become a destination for many former stars of European football.

And Ashworth said there is nothing stopping Newcastle from signing players from the Saudi league.

"The current rules and regulations say there is nothing to stop it," he said.

"There is a potential that the various different organisations will look at things across related parties and what you can do to acquire players at a fair market value, which have already been in place for a quite a while."

Tonali, meanwhile, has been cleared to resume training during what Newcastle boss Eddie Howe described as a "lonely" process.

"We're playing so many games at the moment that a lot of his sessions will be individual or small numbers," said Howe at his pre-match press conference ahead of Saturday's visit of Arsenal.

"He's started that journey into the 10 months so it's going to be a real mental test for him to try and come through that period and become a better player, which is definitely our objective as coaches to try and help him.

"It's going to be difficult for him for sure."