The Blues confirmed over the weekend that they had agreed a deal with Belgian champions Genk to sign the 19-year-old, who would be Villas-Boas' first signing since taking charge at Stamford Bridge.
Villas-Boas, speaking on arrival in Malaysia where Chelsea will play a pre-season friendly on Thursday, told the club's website: 'At this moment he is having a medical but has not yet agreed personal terms.'
Blue boy: Courtois is edging close to a switch to Stamford Bridge
Courtois was voted Genk's player of the year last season as they won the national title, and was also named Belgian goalkeeper of the year.
Courtois made his league debut for Genk in April 2009, aged just 16.
The club added: 'It is not expected that he will join up with the squad in Asia should the transfer be completed in time.'
Following the match against a Malaysia XI in Kuala Lumpur, Chelsea move on to Bangkok to take on the Thailand All Stars before travelling to Hong Kong for two matches in the Barclays Asia Trophy.
Straight talking: Villas-Boas is leading Chelsea on their tour of Asia
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Source: Daily Mail
Source: Daily Mail