Chelsea will pay a world record fee for a goalkeeper to secure Kepa Arrizabalaga from Athletic Bilbao as a replacement for the outgoing Thibaut Courtois, who failed to report for training for a second day in succession and is expected to sign for Real Madrid this month.

Kepa, capped once but considered one of the most promising goalkeepers in Europe having impressed for his country through the junior age groups, has a release clause set at €80m (£71.6m). Bilbao are braced to lose the 23-year-old, who has travelled to Madrid with his agent before a 10am flight to London on Wednesday morning, having come close to selling the youngster to Real for only £17.9m in January.

Thibaut Courtois fails to report for Chelsea training for second day running Read more

The goalkeeper even passed a medical in the mid-season window only for the then Real manager, Zinedine Zidane, to dissuade the board from pursuing a deal as he was wary of disrupting the team’s rhythm by changing goalkeeper halfway through the campaign. Bilbao ended up tying him down to new terms, including that eye-catching buy-out clause, before finishing 16th with Kepa, who had joined the club at the age of 10, making 30 La Liga appearances en route.

By triggering the clause, Chelsea would eclipse the £66.9m Liverpool paid Roma for the Brazil No 1, Alisson, last month. Kepa is expected to undergo a medical on Wednesday and could even make his debut in Saturday’s Premier League opener at Huddersfield. “I saw him one year ago [when I was] at Naples, and my first impression was he was a very good goalkeeper,” said Sarri after Chelsea’s goalless draw with Lyon on Tuesday night. “Very young, but very, very good.”

Play Video 0:58 Chelsea manager Maurizio Sarri on Courtois, Kepa and Hazard speculation – video

The move still constitutes a surprise, not least because Chelsea, too, looked into signing Alisson earlier this summer but were apparently put off by the size of the fee. Yet the London club, who had also considered cheaper options such as Jack Butland and Sergio Rico of Stoke and Sevilla respectively, have more leeway on the fee given their desire to add another body in midfield is close to being resolved with the signing of Real’s Mateo Kovacic on loan.

The Spanish club have offered the unsettled Croatia midfielder as a sweetener to ensure their pursuit of Courtois reaches a positive conclusion. Kovacic has made clear a desire to play more regularly and will be permitted to leave for the season. Chelsea would not have an option to make the move permanent next summer, with Real considering him a long-term successor for his compatriot, Luka Modric. That deal, too, could be confirmed on Wednesday.

Courtois, who had been due to resume training at Chelsea on Monday following an extended break after the World Cup, was absent without leave at Cobham again on Tuesday with the club having now written to him formally requesting him to return.

The Belgian, who has entered the final 12 months of his contract, had made clear in a telephone conversation with Sarri last week that he wants to return to Madrid, where he spent three years on loan at Atlético. His two children live in the Spanish capital with the player’s former partner. That move can be completed any time before the end of the month.

Kovacic, a £27m signing from Internazionale three years ago, has found opportunities limited at the Bernabéu and made only 10 La Liga starts last term. He would most likely play alongside Jorginho and N’Golo Kanté in Sarri’s favoured 4-3-3 system and his arrival could yet see Chelsea attempt to shift at least one of their fringe midfielders, Danny Drinkwater or Tiémoué Bakayoko, who both started against Lyon.

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Clubs have been put off to date by the loan fees that would be involved, with some prospective suitors quoted eight-figure sums plus the entirety of the player’s wage to take them on for the season. Bakayoko could yet join Milan for the season.

Ruben Loftus-Cheek played 59 minutes against Lyon, who were beaten 5-4 on penalties with 38-year-old Rob Green saving from Pape Cheikh Diop, and is keen to remain at Chelsea for the season ahead. “He’s potentially a great player,” added Sarri. “He has to improve from the tactical point of view. But I think that’s not a problem. He’s very young. He can be a very beautiful player for us.”