The Blues boss singled out the South African winger ahead of Wednesday's trip to Manchester United.
Martinez is quoted in the Liverpool Echo as saying: "He's such a special footballer and what he brings to us into the way we play is quite unique. Stevie's experience is a valuable part of his squad and it's real bonus to have him back at his best.
"Not many players have his appreciation of space and close control, or the quality in one versus one situations when he opens the spaces and allows other players to come in.
"He has that composure and time on the ball, and slowly he's regaining his full fitness and he'll get back to his best."
Martinez's side are currently fifth in the Premier League.