The Brazilian forward was one of the standout performers last term before his campaign was ended prematurely by a knee injury in July.
But Martinelli could be back in under-23 action later this month.
"Gabi is another one that even in a moment of adversity, you see him training and everything he brings to the team, his energy, his passion, his motivation, is translating positive emotions to everybody," Arteta said this morning.
"He tries and goes and goes again and he wants to score a goal. He's ruthless in training in every single action and the more players and staff you have to add that, at the end that gets translated to what happens on the football pitch and over time you will be stable.
"Gabi's pressing brings something different to the team and we need players like him."
He continued: "Time is the key word in this industry, and nobody is going to give you time! The moment the ball doesn't go in the net and you lose a football match, you're going to question all the rest, so with Gabi it's the same. Now he needs time.
"He's done it for a period of time and in certain moments throughout a game, but consistently for three years, two or one? He's never done it. I'm sorry, he's never done it, so we cannot put that pressure on him.
"It's like with Bukayo and other young players that we have, they've never done it in their career, so why do you expect him to do it today? And in which environment? In which context? Patience, but he's a positive guy to have back on the team because he's such a character."
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