• Raúl Sanllehí to become Arsenal’s new head of football • Vinai Venkatesham to assume new role as managing director

Ivan Gazidis is to leave Arsenal to become Milan’s chief executive. The 54-year-old, who has been at the club since 2009, described the move as “the hardest decision” of his life.

Gazidis will leave Arsenal on 31 October before taking up his new post at San Siro on 1 December. Arsenal will not directly replace their chief executive. Raúl Sanllehí, the head of football relations, is to become the head of football, while the chief commercial officer, Vinai Venkatesham, will take over the role of managing director.

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Gazidis oversaw the process to appoint Unai Emery to replace Arsène Wenger in May and has also been behind the change in management structure, playing a major part in introducing roles such as Sanllehí’s, as well as that of the head of recruitment – held by Sven Mislintat.

Those appointments wrestled some power away from Wenger, whose 22-year tenure came to a close at the end of last season. Emery has since taken the reins after a thorough interview process headed by Gazidis.

He explained his decision in a message to Arsenal supporters having opted to take up a new role under Milan’s American hedge fund owners, Elliot Management.

“I know many will think this is a strange time to be leaving but I believe it is the right time for me and for the club,” Gazidis said.

“Change and succession is not only inevitable for a club like Arsenal, it is necessary if it is continually to keep moving forward.

“ One of my primary responsibilities as chief executive has been to make sure there is good succession planning in every position in the club, including my own.

“Although it is very hard to do – the hardest decision of my life – I believe that, after 10 years, it is the right time to step aside to allow new leadership, energy and ideas to take the club forward into this exciting new era.”

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Stan Kroenke last month launched a bid to take overall control of Arsenal through his company Kroenke Sports and Entertainment.His son, Josh Kroenke, who is the deputy chairman of KSE, praised Gazidis.

“It has been a pleasure working with Ivan. We will miss the wisdom, insight and energy he brought to our club on a daily basis over the past decade.”

“We are confident we have outstanding people in Raul and Vinai, and we look forward to working with them and Unai Emery to continue to move the club forward on and off the pitch.Milan, who were sold to Elliot in July after the previous owner Li Yonghong defaulted on a loan, first approached Gazidis in the summer. He is expected to hold talks with Uefa over financial fair play after Milan had a ban on playing in the Europa League overturned by the court of arbitration for sport.

“In hiring Mr Gazidis Milan brings on board a world-class football executive,” the club said.