Chelsea reportedly kept close tabs on teenage attacker Alexander Isak in action for Willem II earlier this month.
Isak was rumoured with a number of teams before making the switch to Borussia Dortmund from AIK back in January 2017.
The forward has only found back of the net once in 13 games for Borussia Dortmund, though, before making the switch to Dutch outfit Willem II on loan during the January transfer window.
The 19-year-old has scored 11 goals in 11 Eredivisie games in the second half of the 2018-19 season, and it has been claimed that the Catalan club are planning to make a summer swoop.
According to The Mirror, though, the Blues watched the striker score for Willem II against Ajax earlier this month and the Blues are now tracking the four-time Swedish international who has been compared to his compatriot Zlatan Ibrahimovic.
The Premier League giants are currently waiting to learn whether their appeal against a two-window transfer ban will be approved.
Meanwhile, Chelsea have told French midfielder Tanguy Ndombele to wait a year and sign for them instead of making switch their direct Premier League rivals Manchester United.
The Lyon versatile midfielder is one of the most wanted players at the moment and hosts of European teams are eyeing move for his signature.
Liverpool, PSG, Bayern Munich and Real Madrid. L’Equipe claim that the Red Devils have held talks with Ndombele, who Lyon value around £80m according to the sources from Britain.