The midfielder missed a large chunk of the last campaign after undergoing ankle surgery as the Gunners finished fourth.
However, the England international has now returned to fitness and Walcott explained how vital he was to the Gunners’ hopes.
"It's so important for the club that Jack stays fit," Walcott told reporters.
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“He's had so many injury problems at such a young age and now we hope they've gone out of the window.
“Without a doubt, he's going to make our team better. He can spot anything when you're making your runs. We're definitely going to have a very good season together."
Walcott also insisted he wanted to help end the club’s trophy drought, with Arsenal having failed to win any silverware since lifting the FA Cup in 2005.
"I'm determined to win something at this club, just to repay the manager for the belief he has and the faith he shows when he brings in players at such a young age," he added.
"He puts young players in there and just says: 'Go and do your thing.' He's given me the chance to go from playing in the Championship to playing in the World Cup. I've had my ups and downs but it's definitely on the up now and I'm very excited."