The Blues paid £23million to bring the defender to west London from Fiorentina.
And on the pitch, Alonso has been a revelation having adapted expertly to his role at left-wing back.
The former Bolton and Sunderland man has started every Premier League game for Chelsea since the start of October.
Marcos Alonso says he and Chelsea team-mate Pedro spend time together away from football
Pedro is a very good friend and I like to catch up with him after training
Off the pitch, meanwhile, Alonso has built a close friendship with fellow Spaniard Pedro.
“Pedro is a very good friend and I like to catch up with him after training,” Alonso told the club’s official website.
“I didn’t know him before I came here but he’s been a great help since I arrived.
Chelsea duo Marcos Alonso and Pedro attended the NBA in London together last month
Chelsea unveil new snaps of Marcos Alonso in Blues kit
Wed, August 31, 2016
Express Sport brings you all the best snaps as Chelsea officially unveil their new signing Marcos Alonso
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Chelsea unveil new signing Marcos Alonso
On the whole, Marcos Alonso has impressed and settled well at Chelsea
“We go for dinner quite regularly and we went to the NBA at the O2 together. I’m not a massive basketball fan but I follow some of the Spanish players.”
The Chelsea attacker has also enjoyed a solid campaign, having established himself as a member of Antonio Conte’s first XI.
Alonso and Pedro could both feature on Saturday (5.30pm) when the Blues return to action at Wolves in the FA Cup fifth round.