Chelsea will reportedly sell Marcos Alonso to Atletico Madrid this summer if the Spanish club are willing to meet their £54 million valuation of the defender.

AS (h/t Metro) reported on the figure at which the Blues would be willing to do business, with Los Rojiblancos' incumbent left-back Filipe Luis reportedly attracting interest from Paris Saint-Germain.

Alonso scored one goal and assisted another in Chelsea's 3-2 win over Arsenal on Saturday, but new manager Maurizio Sarri is said to be willing to sell the player if the offer is deemed too good to turn down.

If there was a game in which the Spaniard underlined what he brings to Sarri's side that other left-backs cannot, this was it early on in the season, per Squawka:

The Premier League transfer window closed on August 9, meaning Chelsea will be unable to bring in a replacement if they sell Alonso.

Emerson Palmieri is the only other natural left-back in Sarri's squad—signed from AS Roma in January—but the Italian has yet to be handed a substantial stretch of starting opportunities at Stamford Bridge.

Chelsea signed Alonso from Fiorentina in August 2016 for a reported £24 million, per Sky Sports, meaning the club stands to more than double their investment should Atletico meet their valuation of the player.

Sports lawyer Jake Cohen hailed the impact Alonso has had at Stamford Bridge after arriving as a late signing during Antonio Conte's first summer at the club:

Sarri would require a surprising amount of faith in Emerson's talents to sanction the sale of Alonso, who's one of the best left-backs in the Premier League, if not all of Europe.

Atletico have a little more than a week to sort out their left-back situation, and La Liga writer Simon Harrison pointed to some factors that mean a sale to PSG would make sense:

Cesar Azpilicueta also could revert to left-back in the latest leg of his defensive merry-go-round at Stamford Bridge, having moved back to the right side of defence from centre-back.

Alonso could be one of the major Premier League departures if he were allowed to leave despite the Premier League transfer window's being closed, with Chelsea open to a sale as long as their valuation is met.