Okay, it's a cliche and it's really a hangover from the past  where centre backs were often the epitome of brute strength and ignorance.

These days they have to be able to play a bit, and they definitely have to be quick and sharp over the ground.

Increasingly, all over the world, we are seeing midfielders converted and used as central defenders;  players who are not tall or imposing but whose game sense and technical ability allows them to get into good defensive positions and play their way out of trouble when they get the ball.

At the highest level a man like Barcelona and Argentina's Javier Mascherano is the best example. At 175 centimetres he is far from big, but his positional sense and game awareness makes him more effective at the back than some of his taller counterparts.

Years before Mascherano came along, Paul Parker performed a similar function for Fulham, Queens Park Rangers, Manchester United and England in the 1980s and '90s.  The 170cm Parker was quite often deployed in the heart of the defence alongside a much taller stopper, with the small man able to use his pace and defensive nous to do the job.

In the A-League, Melbourne Victory  uses 170cm Leigh Broxham as a key defender for similar reasons.

Necessity in all these cases is usually the mother of invention and it certainly has been at Melbourne City, where John van 't Schip is set to pull a similar move for the second week in a row when he uses 174cm midfielder Jacob Melling as a central defender.

With Patrick Kisnorbo and Aaron Hughes still missing, Melling was thrown in at the back alongside Connor Chapman last Friday night for City's daunting trip to Brisbane.

He did pretty well, Brisbane's equalising goal aside, when Henrique lived up to his "Slippery Fish" nickname and got away from Melling long enough to convert Thomas Broich's cross to make the score 1-1.

Melling performed well enough for van 't Schip to persist with him in the heart of defence again this Friday when City host Perth Glory at AAMI Park.

"Even if I wanted to change things I can't," the coach said.

"But I think Jacob and Connor did well and Jack [Clisby] did well as a left full-back. I think we will continue with that and hope to build on that.

"Jake has shown he has the quality. He is not big, but he is strong. He can jump high. It's another way of defending. You can't just step out in the midfield to take a big risk to find and try to get the ball.

"Now [playing as a centre back] you have to really judge in a different way, because if you step out now and you miss, it's mostly a very dangerous situation. He coped very well with doing that [against Brisbane], so hopefully he can show it again and take another step."

Van 't Schip knows that Perth, who beat City 3-1 in the FFA Cup semi-final in Western Australia earlier this year, are physically strong with big defenders and are particularly threatening from aerial plays at set pieces.

But that is not the only way that they can hurt his team.

"They have some individual players that are good like [Diego] Castro; he can have moment in a game where he can decide things. [Nebojsa] Marinkovic we know has a good killer pass. Michael Thwaite's playing in a different role in the last games, from out of the middle. He has a good shot and can come into the box for crosses.

"It's not only about set pieces. In general we know that they are strong and they build their performances around a solid structure. Their full-backs like to go forward, they defend but when they have the ball [Josh] Risdon and [Marc] Warren like to go forward and assist the attack."

Ivan Franjic, the Socceroo full-back, made his A-League debut for City last Friday after a long injury absence, coming off the bench in the second half against the Roar. He will start this time but otherwise van 't Schip is unlikely to make many other changes.

He is happy, however, that he has got Harry Novillo and Corey Gameiro back to something like match readiness so they can take their place alongside Uruguayan striker Bruno Fornaroli. The trio linked for the first time in the game against Brisbane, when Novillo put City in front.

"They are three different kind of players but the only one that's really 100 per cent at the moment is Bruno. Physical and also mentally.

"Harry and Corey are coming back from long-term injuries, especially Corey. That's going to take a few weeks but if you don't play them it's not going to happen. We're happy that we're fit and we can make use of them again. It's about during the week, managing and trying to get them to the level that they can play 90 minutes.

"Our young players, we use them a lot - Steve Kuzmanovski, Stefan Zinni, Wadey Dekker - not only in the start of the league but also in pre-season, now it's time for those boys to watch and be prepared when they have to come in maybe."

City's fans have seen them crash twice at home in their past two outings, shipping three goals each time. Van 't Schip knows the pressure is on to deliver at AAMI Park.

"We are disappointed about the last games and we want to set that right. The only way to do that is get a win against Perth. Everyone understands that."