The Chelsea manager is taking his Premier League title rivals very seriously, arguing that their promising young players have grown up and been joined by experienced heads
The Gunners have gone eight years without winning a trophy as Arsene Wenger has prized youth development over spending large sums of money to acquire established talent.
But the north Londoners now lie just one point behind Premier League leaders Chelsea with 12 games left, and Mourinho interprets this as a sign that their talented youngsters have come of age.
"Arsenal have spent many, many years working together, making these players grow up and achieve this maturity level," the Chelsea boss told the Daily Mail.
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"The manager, with this group of players ... four, five or six years working with these players and then adding fantastic players like Mezut Ozil, Santi Cazorla or Per Mertesacker to the team, these last pieces of experience. I think they are a very good team."
Chelsea are set to face Manchester City for the second time in 12 days on Saturday when they travel to the Etihad Stadium for the FA Cup fifth round and Mourinho feels that, despite two wins against Manuel Pellegrini's men so far this season, the hosts will be "favourites".
He declared: "We have got a very difficult draw in the FA Cup. We play in the home of the best team in the country but we have beaten them twice.
"If people were saying that, the last time we did it, there was no Fernandinho and no Sergio Aguero: the first time we beat them, they were playing. But that makes it even more difficult to beat them for the third time.
"The draw has opened the competition up for a smaller team to reach the final," he added. "Two big teams are going out in the quarter-final, with us drawn against City and Liverpool against Arsenal. It opens the door completely.
"And imagine if, in the semi-final, we play the winner of Liverpool v Arsenal. It is fantastic because the cup belongs to everybody. We have a difficult job of playing [away against] the favourite."
England manager Roy Hodgson dismissed speculation of a recall to the international setup for centre-back John Terry on Wednesday and Mourinho is happy not to wade into the debate.
"It's a waste of time to keep speaking about the situation," he stated. "Roy Hodgson is the person to kill the discussion or to feed it. End of story.
"I'd never intervene. He's in charge and has everything in his hand. He has made that decision.
"For me, as a Chelsea manager, I'm happy players play with their national teams but, at the same time, I'm happy an important player like [Terry] is fully focused on his work at Chelsea."