That’s the opinion of Sunderland legend Niall Quinn, who believes the 25-year-old is the main reason Antonio Conte’s new tactics have proven to be a success.
Alonso joined Chelsea from Fiorentina on transfer deadline day for £23m and has slotted straight into the Blues setup.
Quinn told Sky Sports: “The 3-4-3 is what goes down in the team sheets that appear in the papers and on the TV screen before games but when Chelsea attack now Marcos Alonso becomes a winger and when they defend he is a left full-back.
“[Chelsea new boy Marcos] Alonso has also freed Eden Hazard up on the left side of a front three”
Sunderland hero Niall Quinn
“He has more mobility than Ivanovic and he suits the new style.
“His versatility means that David Luiz can do the things he is good at, like moving the ball forward quickly and also be well covered when attempting the things he is not so good at, like old fashioned defending.
“Alonso has also freed Eden Hazard up on the left side of a front three.
“Hazard is part of the new theme at Chelsea right now.”
After the emphatic 4-0 win over Manchester United yesterday at Stamford Bridge, Chelsea find themselves just one point off the top of the Premier League table.
Next up for Conte’s side is a trip to West Ham in the EFL Cup on Wednesday evening.