The Blues were thoroughly out-played by the Gunners as the north London side secured a 3-0 win over Antonio Conte’s men at The Emirates back at the start of the season.
However, Chelsea were able to bounce back from the defeat and produce a brilliant run of form to win the Premier League title in Conte’s first season in charge at the club.
The Blues also inflicted revenge on Arsenal by beating the Gunners 3-1 in the reverse fixture at Stamford Bridge later in the season.
But full-back Azpilicueta still considers Arsene Wenger’s men to be the toughest team the Blues faced last season.
Asked who Chelsea’s toughest opponents were last season, Azpilicueta told the club’s website: “When we played Arsenal away.
“In the first half they were better than us and that is why they were 3-0 up.”
Chelsea are preparing to kick off their Premier League title defence as they look to retain their crown in Conte’s second season in charge.
The Blues are also set to make a return to the Champions League next season after they won the title last term.
MORE: Man United latest news
MORE: Arsenal latest news
MORE: Chelsea latest news
MORE: Liverpool latest news