Oblak, 27, is arguably the best keeper in the world and is regularly compared to Liverpool and Manchester City’s first-choice stars Alisson and Ederson.
The Slovenian would however cost in excess of £100million due to a release clause in his contract, while 24-year-old Onana’s price-tag is less than £30m.
It is unknown how much Burnley would demand for England international Pope but the 28-year-old has been sublime for the Clarets this term.
His tally of 15 clean sheets from 38 Premier League appearances was only bettered by City’s Ederson, who managed 16.
Neuer is by far the oldest option of the quartet and if Chelsea are looking for a player to command the gloves for the foreseeable future, they are presumably more likely to go for a younger alternative, although keepers are well capable of playing up to the age of 40.
Caballero – who has signed a one-year extension to stay at Chelsea – has urged Lampard to keep the faith with his team-mate Arrizabalaga and said: “Of course I hope he stays.