Mario Pasalic has agreed a new deal to extend his stay at Chelsea until 2022.
The 24-year-old midfielder will, however, return straight away on loan to Atalanta for a second consecutive season.
Last year, the Croatia international represented the Italian side on 42 occasions, helping them secure their best Serie A finish of third. He scored eight times.
Pasalic joined Chelsea from Hajduk Split in 2014, before being sent on loan to Elche, Monaco, AC Milan, Spartak Moscow and Atalanta.
He has also played 10 times for Croatia, featuring in their recent European Championship qualifying double-header against Wales and Tunisia.
