According to the same story, Unai Emery has a mere £45m to spend on new signings this summer hence why Arsenal have made a conservative offer for the highly-rated Scotsman.
It would make complete sense for the Gunners to part ways with Monreal and bring in a fresh player to add to their left-back options.
Tierney has always been tipped for big things; both on the global stage and in European competition with Celtic, he has looked at home, and £25 million is by no means an unfair valuation.
The 22-year-old made his first-team debut in 2015 at the end of the 2014-15 season, and became a regular player for the club from the very next season, and is now one of the most important players in the Celtic squad.
The Gunners have already seen a bid of their rejected by the Bhoys as it fell short of what Neil Lennon's side have been demanding for the youngster.
But despite that, Tierney is apparently in no hurry to leave his boyhood club in order to chase the fame and riches on offer down south.
A move to the Premier League would make sense for him at this point, despite it breaking the Parkhead faithful's collective hearts.