Martinez has been at the Emirates for almost 10 years, struggling for game time at the north London club getting shipped out on six loan spells.
That all changed when Leno got injured in the defeat to Brighton in June and his deputy was forced to step up into the limelight.
The 27-year-old enjoyed an excellent run of form all the way through until the end of the campaign and helped fire the club to their record 14th FA Cup win.
Now, Mikel Arteta has one of the toughest choices of his managerial career to make in picking between the now fit Leno and in-form Martinez.
Martinez got the nod in the Community Shield win over Liverpool on Saturday, but it remains to be seen who will be between the sticks for the Gunners’ Premier League opener against Fulham on September 12.
When asked who should start in goal for the upcoming campaign, Campbell told Stadium Astro: ‘What I’ve seen from Martinez, I would go with Martinez, because I think he makes that defence a lot more settled.
‘They don’t panic when he’s behind them. I’ve seen them panic when Leno’s there.’
‘Leno they brought him in, paid big money to Leverkusen, he’s come in and done fantastic.
‘But at the end of last season when Martinez came in, he looked the part he performed. He’s now won two bits of silverware, Leno’s won no silverware.
‘He’s made some key decisions, his handling is very good, he comes out and makes people feel comfortable from crosses.’