Andy Murray is not getting carried away by his perfect start at the Australian Open and insists he can play even better.

The British number one has barely broken sweat in his opening two rounds in Melbourne after sailing past Germany's Alexander Zverev 6-1 6-2 6-3 and then thrashing Australian Sam Groth 6-0 6-4 6-1 to make round three.

Two assertive displays - and just over three-and-a-half hours spent on court - stand Murray in good stead as he prepares for Saturday's test against Joao Sousa, the 32nd seed from Portugal.

"It's been a very good start, for sure. But I can still get better," Murray said.

"I've had days, not just in slams, but in any tournaments, where I felt great, practised really well, and then gone on the court and felt horrible.

"Then sometimes, beforehand you might feel nervous, have a lot of doubts, and then you go out and play extremely well.

"It's difficult to know as a player whether you're going to go out there and hit the ball great or not, you just have to try to trust all of the preparation and practice that you've done."

There will be tougher opponents to come for Murray, including Sousa, but the world number two has found his rhythm early, particularly against Groth, when he won all of the first nine games.

"I think he's played great," said Greg Rusedski, former British number one and now a pundit for Eurosport.

"We always talk about that Davis Cup win for Djokovic, when he went on to have his best year in 2011, the same thing's kind of happening for Murray at the moment.

"He's growing in confidence, he's growing in stature. If you look at his game, everything is firing."

Murray should have few problems against Sousa, having beaten the world number 33 in all of their past six meetings, most recently in the French Open second round last year.

Sousa took a set and temporarily flustered Murray at Roland Garros but the Briton recovered his composure to seal a comfortable victory.

"He's almost the opposite to Groth really," Murray said.

"He plays predominantly from the back of the court. Very solid from the baseline, doesn't obviously serve so big but makes a lot of returns.

"So if I play well, I've got a good chance obviously. But he's the sort of player that if your level's not quite there, he'll make it very tough for you, as he did when I played him at the French Open.

"I was in a bit of trouble against him there."

Rusedski is not convinced.

"The question you ask yourself is how is Sousa going to hurt Murray?" Rusedski said.

"Does he have a big serve? No. Can he beat him from the back of the court? No. Does he have the feel of Murray?

"Unfortunately for Sousa he's a solid player out there but solid players don't get it done against the big four, you have to have something big.

"It's going to happen for Andy Murray in straight sets."

Sousa, however, has been gaining in confidence after spending his off-season training with the notoriously relentless Rafael Nadal and seeing instant benefits, with two convincing opening wins against Colombian Santiago Giraldo and Kazakhstan's Mikhail Kukushkin.

He has already played Murray twice at the Australian Open - in 2013 and last year - and lost in straight sets on each occasion.

"I am playing very good actually. I played much better in the second round than the first. I felt unbelievable on court," Sousa said.

"I played Murray last time in Roland Garros and I took a set off him which was very good. I think I played well and I have been playing better and better against him.

"In Portugal we have a saying 'the third is the one' so perhaps this is my time."