The Blues, who have already agreed personal terms with the 28-year-old, are finalising a move worth about £16.3m plus further add-ons, with all parties increasingly confident about striking a deal.

Left-back Chavarria is a key target for new manager Xabi Alonso having faced him while he was in charge of Real Madrid last season.

It has been almost a month since Chelsea had an initial £15m bid rejected by the La Liga club when talks began at the end of June.

Negotiations became protracted amid a belief at Chelsea that Rayo were raising their valuation during the process, asking as much as the full £42.8m release clause at one stage.

Chavarria made it clear to Rayo, who lost to Crystal Palace in the Conference League final in May, that he wanted to move to Stamford Bridge.

Alongside new right-back Marco Palestra, who joined Chelsea for £47m from Atalanta in July, Chavarria's arrival would give Alonso the chance to replicate his wing-back system that helped Bayer Leverkusen win the Bundesliga title in 2024.

His signing also adds depth to the left-back position after Marc Cucurella joined Real Madrid in June for £51.8m.

It is also another player with experience added to the squad, along with the signings of striker Danny Welbeck, 35, from Brighton and Jordan Henderson, 36, after he cancelled his contract with Brentford.

Chelsea have also signed club-record £117m forward Morgan Rogers from Aston Villa and defender Maxence Lacroix from Crystal Palace for £52m, with midfielder Valentin Barco expected to join from partner club Strasbourg imminently.

They are expected to focus on player sales in the coming weeks having reached an agreement to sell Trevoh Chalobah to Italian club Como 1907 for about £31m.