According to Daily Mail, Gunners are being kept updated with regards to the former Valencia man's future with a view to launching an audacious swoop should Chelsea decide to sell.
Manager Arsene Wenger came close to landing Mata in 2011, but Chelsea pipped the Gunners to the 25-year-old.
Mata has become one of the Premier League's best ever imports, winning the Champions League, Europa League and FA Cup since his arrival.
Chelsea insist the player is not for sale this summer, but Arsenal will continue to watch the situation carefully should their stance change.
Reports emerged earlier this week that either Mata or David Luiz could be used as makeweights in Chelsea's move for Manchester United striker Wayne Rooney.
But Mourinho rubbished the prospect, saying there was 'no chance' either player would be sold this summer.
“I spoke with them during the summer but when they finished the Confederations Cup I wished them luck and told them I will see them on July 28,” said the Chelsea boss.
‘I have told them they are very important for me. How can I change that two days later? So, no contact with them.’
Mata scored 11 Premier League goals last season and notched up 13 assists, earning him the club's player of the year award for the second successive season.
Arsenal are also chasing a number of other targets, with the north-London club hoping to bring any one of Liverpool's Luis Suarez, Manchester United's Wayne Rooney or Real Madrid's Gonzalo Higuain to the club as a marquee summer signing.