The Gunners have confirmed the capture of the 25-year old Chile international who has joined the north Londoners on a long-term deal from Barcelona for around £30million.
Wenger, who is still in Brazil working for French TV at the World Cup, welcomed the former Udinese ace to the club while saying that Alexis will bring plenty of positive attributes to the Emirates Stadium.
"As many people have seen during the World Cup this summer, Alexis is a fantastic footballer and we are delighted that he is joining us at Arsenal," read a statement from Wenger.
"Alexis will add power, creativity and much quality to our squad and we are all looking forward to him joining up with us in a few weeks. He has consistently produced top-quality performances at the highest level for a number of seasons now and we are all excited to see him integrate into the Arsenal squad.
"I'm sure all Arsenal supporters will join me in welcoming Alexis to our club."
During his time with Barcelona, Alexis scored 47 goals and provided 36 assists in 141 appearances in all competitions for the Catalan giants.
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