Alonso has played an important role in our Premier League and FA Cup triumphs, as well as becoming a member of the senior Spain squad, since arriving at Stamford Bridge in August 2016.
After putting pen to paper on his new deal, the 27-year-old said: ‘I am so happy to stay here longer and to keep playing for one of the best teams in the world. It’s been a very good two seasons and I am looking forward to more.’
Club director Marina Granovskaia added: ‘We are delighted to be extending Marcos’ contract. In the past two seasons he has developed into an important player for the club, demonstrating his outstanding ability and a fantastic attitude that has helped him become a Premier League champion and Spain international.’
A versatile left-sided player, Alonso made his debut for the Blues in a 4-2 League Cup win away at Leicester City. His first Premier League start came against Hull City, deployed at left wing-back in a new-look 3-4-3 system. It coincided with the start of a club-record 13 straight league wins, a sequence of results that took us to the top of the table. An ever-present in that run, he became the first player in English football league history to win his first 14 starts for one club.
We remained at the Premier League summit until the end of the 2016/17 season with the roles of Alonso and Victor Moses, the two wing-backs, a huge factor in our title success. As well as making 31 appearances, Alonso chipped in with six goals, including a brace in a 3-0 win at Leicester, the opener in our 3-1 victory over Arsenal and a superb free-kick, which has become his trademark, away at Bournemouth.
Goals continued to flow in his second season as Alonso netted eight times, two of those goals arriving in a 2-1 win away at Tottenham. Included in the brace against the north London side was another stunning free-kick, the first of three he would score during 2017/18, with his ability from dead-ball situations becoming a huge asset for the side.
Alonso’s eye-catching displays at club level led to a senior Spain call-up and he made his debut for the national side in March when he came off the bench in a 6-1 friendly win over Argentina.
He secured the second winner’s medal of his Chelsea career by helping us overcome Manchester United at Wembley in the FA Cup final, and was rewarded for the overall quality and consistency of his displays with a place in the Premier League Team of the Season.
Alonso has been an ever-present in our impressive start to the current league campaign and scored the decisive goal as we beat Arsenal 3-2 in August, as well as winning penalties in our early-season victories over both Huddersfield and Newcastle.
Clearly impressed by the performances of the defender, Maurizio Sarri said Alonso, who made his first start for Spain against England last month, has the potential to become the best left-back in the world.
With a new contract for the next five years, we can look forward to seeing plenty more of Alonso down our left flank.