Thomas Tuchel must keep Chelsea promise to avoid repeating £20m mistake amid FA Cup warning

Chelsea have been left to rue the decision to sell Marc Guehi following the 21-year-old's metamorphosis into one of England's leading centre-halves. The Cobham graduate, who swapped Stamford Bridge for Selhurst Park in the summer for a deal worth just £20 million, was one of many departures that funded a £110m windfall that secured the services of Romelu Lukaku.

Guehi has impressed under Patrick Vieira, completing 90 minutes in all but one of the Eagles' Premier League clashes this season as the south Londoners look to swoop in on new territory. The newly-capped England international has guided Palace into the top half of the Premier League and to a FA Cup semi-final.

Ironically, the young defender has transcended into the perfect candidate for Thomas Tuchel's new-look defence next season. The deal agreed between the London sides includes an opportunity for Chelsea to buy Guehi back for the same fee agreed with another club, according to the Guardian, should the German look to bring him back.

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Despite the west London side's clause that offers a silver lining, Chelsea have paid the price for not investing faith into a returning loanee. Last season, Guehi earned his stripes out on loan at Swansea City in the Championship.

He impressed and guided the Swans to a Premier League play-off place but fell short at the final hurdle against Brentford. Similarities can be drawn between Guehi and starlet Levi Colwill, who's currently learning his trade in the Championship.

According to The Athletic, Tuchel is looking to assess Colwill's development at the end of the season as a route into the Chelsea first-team begins to open up. Antonio