Martin has been criticised for sticking to his playing principles as Saints have struggled.
But ahead of Sunday's game, Postecoglou said: "They've played some pretty exciting and effective football against very good teams.
"Russell will be frustrated they haven't been able to sustain or get rewards for it. The good stuff gets diminished because people invariably look at the outcome.
"That is fair enough but I think some of the football they've played has been as good as anyone this year," he added.
"Their ability to play out from the back, their ability to play through pressure. They've made some mistakes in trying to do that.
"But for the amount of times they've done that really well they probably haven't got the rewards that good play deserves. It kind of skews people's outlooks.
"It's going to be a good challenge for us. They're a good footballing side. There's some opportunity for us there because we're a good pressing team."