Veteran Tim Cahill did the damage on the scoreboard, putting a trademark header past Costa Rica goalkeeper Patrick Pemberton in the 69th minute, taking him level with Damian Mori’s record of 29 goals for Australia.
It was the start of a new chapter for the Socceroos, who despite a nervous start, looked a revived outfit.
They largely delivered the attacking, possession-based game Postecoglou likes to play and didn’t allow the Costa Ricans to get into any real rhythm, with the world No. 31 side not registering a single shot on goal.
Clearly wanting to assess some of the younger players, Postecoglou started Dario Vidosic and Mathew Leckie up front while the likes of Josh Kennedy and Cahill sat on the bench.
And while the duo showed promising signs in attack it was veteran Cahill who finally broke the deadlock in the 69th minute with another vintage moment of aerial brilliance as he climbed past the Coast Rican defence to head home and put Australia 1-0 up.
The Socceroos’ first real chance came just before the break when Robbie Kruse, who was a real thorn in the Costa Rican’s side the entire game, set Leckie up perfectly.
Kruse sent the ball across the face of goal, only for the striker to misfire.
Crystal Palace skipper Mile Jedinak looked like opening the scoring early in the second stanza with a powerful strike but sent it wide.
In an effort to turn chances into goals Postecoglou brought Cahill and Tom Rogic on in the second half and the move paid off.
Celtic playmaker Rogic, despite constantly being fouled, instantly created space and looked dynamic while Cahill was a threat from the get go.
The Socceroos defence, heavily criticised after recent thumpings to Brazil and France, looked the most solid it has in a while.
Lucas Neill, who became Australia’s longest-serving captain by wearing the armband for a 61st time, marshalled the defence well as he partnered with Rhys Williams in the centre of defence.
However Jason Davidson, who’s being touted as a possible long-term solution at the problematic left-back spot, had a night to forget.
He almost put Australia a goal behind early in the match when he sent the Socceroos defence scrambling with a clearance gone wrong, only to be saved by Ivan Franjic who cleared the ball off the line.
It was the only real threat to Mat Ryan’s goal, with the keeper not having to make a save.
Wellington Phoenix’s Carlos Hernandez and Kenny Cunningham came on as second-half substitutes for the Costa Ricans, who were largely left wanting in most aspects of the game.
Socceroos player ratings:-
MATHEW RYAN: Rarely needed as Costa Rica didn’t put a shot on target, but a clean sheet is a clean sheet. Rating 7.
LUCAS NEILL: Some anxious moments but his organisation of an inexperienced defence justified him becoming the longest-serving Socceroos captain. Rating 6.
MARK MILLIGAN: Reliable and hard working in midfield, rarely put a foot wrong in another dependable display. Rating 7.
MATHEW LECKIE: Was clearly out to impress and did so. Played with pace and was a constant threat up front. Rating 8.
ROBBIE KRUSE: Shrugged off heavy marking from the Costa Ricans to be a constant attacking threat. The stand-out. Rating 9.
RHYS WILLIAMS: Started brightly in central defensive posting next to Neill, with some shrewd long passes, but faded before being subbed. Rating 6.
MILE JEDINAK: Solid game alongside Bresciano in the midfield holding role. Found space, created chances and frequently chopped off Costa Rica attacks. Rating 8.
JASON DAVIDSON: Shaky start to his audition to become a long-term solution at left back. Looked a tad green in the role, perhaps trying too hard. Rating: 4.
MARK BRESCIANO: Typically crafty and creative, a solid performer who again proved his class. Rating 7.
IVAN FRANJIC: Eye-catching at right-back. Made some daring forward runs and was sound in defence. Rating 7.
DARIO VIDOSIC: Started nicely but drifted out of the game in an attacking role along the left-flank. Rating 4.
RYAN McGOWAN: Replaced Williams in the centre of defence in the 48th minute. Solid without being spectacular. Rating 5.
TIM CAHILL: Replaced Leckie in the 52nd minute and scored the winner. Remains the talisman. Rating 8.
TOM ROGIC: Replaced Vidosic in the 61st minute and was enervating in midfield, showing superb skills and attacking intent. Rating 7.
TOMMY OAR: Replaced Bresciano in the 61st minute, some nice touches but needs more game time to flourish. Rating 6.
JOSH KENNEDY: Replaced Kruse in the 76th minute. Had little impact, but he remains a point of difference. Rating 5.
MATT McKAY: Replaced Milligan in the 76th minute. Solid, but had few opportunities to impress. Rating 5.