Whether Chelsea are willing to let Belgium number one Thibaut Courtois depart Stamford Bridge for Real Madrid or risk losing him on a free come next summer when his contract expires, he will leave some big gloves to fill.

The goalie, who missed training with days to go before the Premier League transfer window shuts, has already won league titles in his homeland, on loan in Spain with Real's city rivals Atletico Madrid and England during what has been a glittering career to date.

Courtois is a top keeper - like Blues predecessors between the posts Petr Cech and Carlo Cudicini - and had a fine summer at the World Cup in Russia, where Belgium finished third.

Chelsea cannot offer Champions League football this season but, having won three European Cup in a row, Real Madrid certainly can and, despite the departure of iconic head coach Zinedine Zidane from the Bernabeu, are a best-price 10/1 in the outright betting through Oddschecker to make it four consecutive crowns.

With Willy Caballero and fellow veteran Rob Green looking backup options at best, Blues owner Roman Abramovich needs to put his hands in his pockets and fund the purchase of a new number one.What are the pros and cons of the main candidates? Let's take a look...

Butland among best of British but stock has fallen since Stoke relegated

Jack Butland made more saves than any other goalkeeper in the Premier League last season, yet that didn't save Stoke City from relegation. With the England shirt up for grabs following Joe Hart's dramatic fall from grace, Gareth Southgate instead chose Everton counterpart Jordan Pickford as his number one for the World Cup finals.

That suggests Butland's stock is not as high as it might've been and a high-profile mistake on his first start of the Championship campaign against former loan club Leeds United is another worry. Given Liverpool have just paid in the region of £66,000,000 to sign Brazil goalkeeper Allison from Roma, however, a reported £25,000,000 valuation of Butland doesn't look so bad and as a homegrown player he helps to fill that quota.

Oblak expensive but already stepped into Courtois' gloves before

Slovenia stopper Jan Oblak was Atletico's answer when Courtois returned to the Bridge from his three-year loan in 2014. The Belgian hasn't been missed in Madrid because of this more than able deputy and Diego Simeone has kept a relative level of sustained success as a result.

With a reported release clause of £89,000,000, however, Oblak's big reputation would also require Chelsea to spend big. That being said he has already stepped in to fill the void left by Courtois' departure from one club, so there's no reason to doubt him doing so again if that is the route the Blues take.