Chelsea defender Marcos Alonso can become the 'best left back in Europe' if he works on the defensive side of his game, according to head coach Maurizio Sarri.
The 27-year-old put pen to paper on a new long-term contract in west London on Wednesday, tying him to Stamford Bridge until 2023.
Although the ink on the new deal is still drying, manager Sarri spoke in glowing terms about Alonso ahead of Chelsea's Europa League match against BATE Borisov, claiming that the former Sunderland and Bolton star can become the best on the continent.
"I am very happy with him and for him. I think he can be the best left back in Europe," Sarri said, quoted by the Mirror. "But I think also that he needs to improve in the defensive phase because he was used to playing in a back five. And now has to play in a four.
"If he can improve, I think he will be the best left-back in Europe."
Alonso joined the club in 2016 following a big money move from Italian giants Fiorentina. He has gone on to make 92 appearances for the club across all competitions, lifting a Premier League title and an FA Cup.
The former Real Madrid Castilla player also spoke to the media after penning his new contract, adding that Chelsea's current form is 'only the beginning' of what they can achieve under new manager Sarri.
"I have been here three years, I have won two titles, I’m hungry for more and here is where I want to win and keep improving," he said. "When Maurizio came I had only heard things about him but now I can say he is a great manager. But this is just the beginning."