Because if he had, it could have paved the return of Francesc Fabregas, who went on to join Chelsea.
The "big" Premier League signing of the summer thus far is Chelsea's acquisition of former Barcelona midfielder Francesc Fabregas, according to Charlie Nicholas, who expressed his regret that Arsene Wenger did not capitalise on the Spaniard's availability by re-signing the ex Gunners captain.
Considering the glut of creative and/or attacking midfielders that Wenger has at his disposal in North London, it is understandable why he did not spend £30 million on a luxury signing - he was, after all, not a necessity.
However, had he ratified the sale of Santi Cazorla, then a space in the Arsenal roster would have been freed up and the club would benefit from a younger and superior player.
Cazorla, according to current market valuations, could be sold for £20 million, meaning Fabregas would effectively have cost £10 million.
Nicholas - a 1987 League Cup winner with Arsenal - told Sky Sports: "I was quite disappointed Wenger didn’t re-employ him."
He continued: "I’d genuinely have looked at the package and thought ‘I could sell Santi Cazorla and bring in Cesc’ and that would have been a perfect marriage for me. It wasn’t meant to be."
On the impact Cesc could potentially have by forming a partnership with fellow summer Stamford Bridge recruit Diego Costa, Nicholas said: "When you look at Eden Hazard and Costa, who both run off the ball, Fabregas is one of the best at picking out these runs and loves to play high up the pitch - and I think Mourinho will give him that licence.
"I’m a massive fan."