Real Madrid have long been interested in getting a top quality goalkeeper to man the post for them, as they don't have complete confidence in Keylor Navas' abilities.
For a long time, that interest was David de Gea, as the 13-time European champions made multiple bids to land the Spain number one over the last couple of seasons, with a fax delay infamously hampering his transfer on deadline day in 2015.
Manchester United however held firm onto their man, and Real Madrid have admitted defeat (a rare occurrence) in their pursuit of the 27-year-old and turned their attention to another former Atletico Madrid goalkeeper.
Interest in Courtois surfaced last season, with the Belgium international refusing to pledge his long-term future to 'the Blues', amidst the rumors linking him to Real Madrid.
He has failed up to turn up at Cobhams (Chelsea's training center) on the expected day (Monday), and is the only member of Chelsea's World Cup semi-final and final contingent yet to resume training after their extended three week break.
Courtois was due for talks with Maurizio Sarri within the week regarding his future, and his act of insubordination is a clear sign to the club that he has no interest whatsoever in extending the one year left on his contract.
With just two days to go until the transfer window closes on Thursday, and three days until the resumption of Premier League action, the time is right for Thibaut Courtois to leave Chelsea. Here are three reasons why Chelsea should act accordingly and sell Courtois immediately.
#3 Just one year left on his deal
Thibaut Courtois has just one year left on his current Chelsea deal, and has repeatedly rejected talks for an extension, as Real Madrid's interest in him strengthened.
Chelsea find themselves at crossroads, as if they hold onto him and refuse to budge, Courtois could simply run down the last year of his contract and leave next season for free on a Bosman.
This is a scenario Chelsea would be desperate to avoid at all costs, and would prefer to get as much money as they can from Real Madrid to invest into a replacement goalkeeper.
Selling Courtois is the most logical decision to be taken by Chelsea from a business perspective, as they would likely get a sizable transfer fee from Real Madrid who are desperate to get a goalkeeper, and the club could then reinvest that money into signing a top caliber replacement, rather than lose the Belgian for free next season.
#2 Chelsea need time to get his replacement
New Premier League transfer rules means that all inbound transfer activities in the Premier League cease a day to the commencement of the league, after a vote by the EPL clubs last season.
There is however a snag to the rule, as it only means Premier League clubs cannot purchase, however, other European clubs are still free to buy EPL players, as the continental teams are still governed by the traditional deadline day of August 31.
With just two days left to the close of the window, Chelsea realistically needs to sell Courtois before Thursday, as a failure to do so would mean Chelsea faces two catastrophic eventualities.
The first of the eventualities is that Courtois runs down his contract and leaves for free next season, which as touched earlier is a proposition the club would not want.
The second and more fatal is that Courtois still agrees a move to Real Madrid (before the August 31 deadline), which will mean Chelsea cannot sign a replacement as the Premier League transfer window would have been shut, and 'the Blues' would find themselves having to navigate a full league season without a quality first choice goalkeeper.
Chelsea could however call Real Madrid's bluff by holding onto Courtois and convincing him to sign a new deal as Manchester United did with De Gea, but with Courtois' heart set on a return to Spain, that looks highly improbable.
The best option is for Chelsea to sell Courtois and wrap up a deal for a new goalkeeper in the next 48 hours, with speculations suggesting that the club is ready to trigger Atletico Madrid's Jan Oblak's £89.3m release clause, they are also interested in Stoke City's Jack Butland and AC Milan's Pepe Reina.
#1 Courtois' wish to live close to his family
Courtois spent three highly successful years at Atletico Madrid on loan from Chelsea and despite returning to London in 2014, his children and their mother remained behind in Madrid.
Thibaut Courtois has not hidden his desire to be close to his family, stating numerous times in the past that he would favor a return to Spain owing to family reasons, and this led his agent Christophe Henrotay to advise the Stamford Bridge outfit to sell him so he could live closer to his family.
With the 26-year-old keen on a return to Madrid, given the strength of Madrid's pursuit of him, his dedication to the Chelsea cause would undoubtedly be severed, and Maurizio Sarri would not want to have an uncommitted player within his ranks, hence the need to sell him, coupled with the economic advantage of selling a player with just one year left on his contract.
Chelsea must act fast to prevent the Courtois scenario from degenerating into a messy situation. Selling him is the best option for all three parties involved, Courtois achieves his desire to return to Spain, Real Madrid get the player they want, while Chelsea get a sizable sum for his sale and reinvest the money into a replacement.
This is a decision 'the Blues' must take, and one they should take pretty quickly.