The Spaniard believes that the on-loan Manchester City midfielder does not get the credit he deserves for his displays.
"Gareth is an unsung hero, but teams need someone that has the understanding and the know-how and can gives you the balance in the side," The Mirror quotes Martinez as saying.
"Maybe Gareth would be more appreciated if he was a foreign player. The role he plays just isn't glamorous for some English people to appreciate because they like their midfield players to operate from box-to-box all of the time.
"But Gareth is an example that England can produce footballers with excellent technical quality who also have good tactical ¬awareness.
Martinez's side visit Arsenal on Sunday.