The Gunners were one of the most active teams in the summer transfer window as they brought in a total of six new faces before the start of the new campaign.
Arsenal signed Gabriel Martinelli, William Saliba, Nicolas Pepe, Kieran Tierney, David Luiz and Dani Ceballos on loan as Unai Emery bolstered his squad.
The north London side were also linked with a whole host of other players as they continue their rebuild under Emery.
Delph ended up signing for Everton in an £8m deal in the summer transfer window after having won a second straight Premier League title with Manchester City last season.
And former Arsenal midfielder Merson admits that he was surprised that the Gunners did not make a move to try and sign the 29-year-old in the summer window.
Speaking on Sky Sports’ The Debate, Merson said: “I look at him and wonder why Arsenal didn’t sign him.
“He is better than the midfield three that played against Tottenham.
“He could have played at left back instead of Kolasinac on Sunday.
“I am a big fan of Delph. He can play in certain positions and is an excellent signing for Everton.”
Arsenal will return to Premier League action after the international break when they travel to Watford on Sunday 15 September.
The north London side finished in fifth place and without a trophy last season after they lost the Europa League final to Chelsea FC.
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