The Chile international has scored 18 times in all competitions for Arsene Wenger's side since his arrival from Camp Nou before seeing his playing time limited of late due to injuries.
However, Edu believes Sanchez has found the right club to flourish at after struggling to break into Barca's side towards the end of his spell with the Catalan giants.
"Alexis is a phenomenon," Edu told www.ca2015.com, the official website of the Copa America.
"At Arsenal he has found what I think he was hoping for; to be an undisputed starter and main player, something he was never able to achieve at Barcelona, despite playing well and receiving praise from the press and fans.
"I think at the moment he is among the five best players in the Premier League, there is no doubt about that."
Despite Arsenal occupying a place in the league's top three, manager Arsene Wenger has come under pressure this season, with the Frenchman acknowledging his side are out of the title race and facing an uphill task to stay in the UEFA Champions League after their last 16 first leg defeat to Monaco.
But Edu - who formed part of Wenger's famous 'Invincibles' side that went the 2003-04 league season unbeaten - backed his former manager to improve fortunes at the Emirates Stadium.
"I am sure things will get better. Arsene is a great manager, but I don't think I'm the right person to be analysing his position on the bench," he added.
"He helped me a lot during the five years I was in London.
"Perhaps the club is looking for a balance between the economic and sporting sides, but I can't really analyse things beyond that."
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