His 12th-minute goal was straight out of the Cahill how-to-score-manual - a powerful header from a Josh Rose cross after he shrugged off the attentions of young Newcastle Jets defender John Koutroumbis.

The latter shouldn't feel too embarrassed to be done over by a veteran like Cahill - he joins a stellar cast of Premier League centre-halves, men like John Terry, Nemanja Vidic, Rio Ferdinand and Ledley King who have, over the years, found the Australian too hard to handle.

City could reasonably have been expected to get on with the job in a straightforward fashion from that early point. But they didn't.

Yes, they had plenty of possession, knocked the ball around well, recycled passes, pushed and probed, but didn't score again for 50 minutes - not until Cahill had departed, making way for wide-man Nick Fitzgerald.

Immediately City looked re-energised, doubly so when another skilful winger, Bruce Kamau, entered the fray, and went on to a comfortable 4-0 win.

And that presents something of a selection dilemma for coach Michael Valkanis as the finals loom. How to use their highest-profile player.

Is City more effective with marquee man Cahill leading the line and starting every match, or are they better mixing it up, using the ageing warrior as a game breaker?

It is then that his guile, smarts and winning mentality can be brought to bear on opposing teams - especially if City is behind and chasing a late leveller or seeking to finish an opponent off.

In those circumstances Cahill's aerial ability can make all the difference, as it did in the FFA Cup final when he scored the only goal of the game against Sydney.

On Saturday evening both Fitzgerald and Kamau ran at the backpeddling Newcastle defenders and injected pace on the flanks, cutting in and looking to set up chances for Bruno Fornaroli, in Cahill's absence free to be the marauding forward presence he was at the point of City's attack last season.

Fitzgerald added a second goal from a beautifully worked move with Anthony Caceres, lobbing over Jets goalkeeper Jack Duncan after a backheel and a run into the area.

Not to be outdone, Kamau's twisting run and dribble into the penalty area drew a foul from Daniel Mullen which Fornaroli slotted away for his 16th goal of the season, adding another later in the match to leave him one behind Melbourne Victory's Besart Berisha.

Cahill now joins his international teammates for the difficult away-World Cup qualifier against Iraq next week before returning to Sydney for the March 28 match against the UAE. He will miss next weekend's A League game against Western Sydney.

Cahill is being paid an enormous sum of money-with some contribution from the FFA's marquee fund - so there is an expectation from the footballing public that he should start in most matches. City say that Cahill's impact on the team goes beyond his on-field contributions, and that his experience and know how is an important factor in building a winning culture in the dressing room.

Valkanis is certainly aware of the conundrum he faces with regard to Cahill.

He paid due tribute to his marquee player's efforts, particularly his goal in the opening-half, in his post-match press conference. But he also spelled out why he needed to change things in the second half to get the direct service from the flanks that he wanted in the first 45 minutes.

"There was a different strategy from the first half which I think worked OK," he said. "We didn't quite execute it perfectly because I think if we played out wide to Ivan [Franjic] we probably would have had more chances on goal. But we kept looking to play vertically in the midfield.

"The first half was good and the goal came from this strategy, and Tim finished it off perfectly. At some point in the second half, the plan was to inject two speedy wingers who were fresh. It worked to a tee.

Cahill has not started every match for City this campaign but when

has got on with the job 14 times (from 23 matches) and come off the bench four times. He has been substituted out of the game on nine occasions, so Saturday night's experience was not new.

His eight goals makes him the club's second-highest scorer this season (behind Fornaroli, who has started in 22 of 23 games), and many of his efforts have been critical - especially his world-class effort in the first Melbourne derby, when he struck from distance, and that header to win the Cup.

Cahill still has what it takes, especially in the air, and can terrorise defences at this level when he is sharp, fit and fresh. He struggles to do it for 90 minutes, but he will be invaluable for City in its finals charge.

Valkanis' challenge will be to work out whether to use him from the start and take him off after a half, or an hour, or bring him him into the fray to seal the deal in close games, which is most often how Socceroo coach Ange Postecoglou uses him.