The tough-tackling midfielder is on England duty and mulling over his future after West Ham's relegation.
Merson told The Sun: "He was the best midfield player in the country last season. Arsenal need to buy players who are going to perform now, not in two or three years because really they haven't got two or three years to spare.
"He might be 30 but you know in the next two years he's going to bring a trophy to Arsenal because of his energy. He'd also help bring along Jack Wilshire too.
"That's the kind of player who I'd be looking at. He would come in and hit the ground running and it won't be, 'Oh well, next year he'll be better'. Arsenal don't have next year."