With great performances in the past 2 years, the 27-year-old Spanish full-back Marcos Alonso has created another archive to remember for the future. Alonso's new deal with the club will keep him at Stamford Bridge till 2023. Joining the Blues in 2016 from Fiorentina Alonso won the Premier League title in his first season at the club. Chelsea boss Mauricio Sarri believes that Alonso has the potential to become the best left back in the world but needs to improve more defensively as he was used to playing in a five-man defensive unit while currently under Sarri it is a four-man defensive line up. Alonso has scored 15 goals in 92 appearances in all competitions for Chelsea and received his first international call-up for Spain in March.