Andy Murray can award himself a straight A after taking the shortest route into the second week of the Australian Open.

There were plenty of doubters, the Scot among them, when Murray began his campaign at Melbourne Park having played just two competitive matches since back surgery.

His first-round performance against Go Soeda was exemplary, his second against Vincent Millot a little less so, but winning 23 straight points in a row was a sensational way to finish.

Both players are ranked outside the top 100, so a third-round meeting with 26th seed Feliciano Lopez was a different matter entirely, even if Murray had won all seven of their previous matches.

But the world number four proved himself more than up to the test, playing a superb tie-break at the end of a tight first set on his way to a 7-6 (7/2) 6-4 6-2 victory.

Murray said: "Today was a big step up for me. Feliciano is a top-30 player. He's a tricky opponent to play.

"I know I have a good record against him, but it doesn't change the fact he's not an easy guy to play against. He's a very different type of opponent to what you normally face.

"So it was a good test for me, and I did well."

Murray loves playing left-handers and players who come to the net, but he did not make a great start, dropping serve in the first game.

He hit straight back, though, and it was Murray creating the chances to forge ahead.

Lopez was frustrating his opponent with big serves, including when Murray forced two set points in the 12th game, but in the tie-break there was nothing the Spaniard could do.

Murray put his foot on the accelerator straight away in the second and third sets with breaks, and Lopez seemed resigned to his fate well before the match was actually over.

The way the British number one stepped up his game in the tie-break was particularly impressive, and he said: "When you haven't played loads of matches, in those moments there's a tendency to make poor decisions or maybe rush sometimes.

"I tried to slow myself down a bit and thankfully I came up with some good shots in the breaker.

"The tie-break was obviously pleasing, but at the beginning of the second set I did well to get a break straight away. And also at the beginning of the third set as well."

Murray went under the knife in September after struggling with the back problem on and off for 18 months and the early signs are positive.

The 26-year-old looked a little uncomfortable in the opening set in temperatures 20C cooler than when he played on Thursday, but he said: "It's pretty good so far.

"I've recovered well after the matches. From time to time there's a bit of stiffness and soreness, but for the most part it's been good.

"You normally are going to get some stiffness in an area where you've had surgery. It takes a bit of time for that to go away."

Murray was keen to pay tribute to his fitness trainers and physio, who worked with him for three months to get him in shape to contest a grand slam.

"When things go well on the court, we talk about the coaches, how good a job they're doing, how hard I've worked with them," he said. "But the guys that are on my team have worked extremely hard to get me back on the court.

"They deserve a lot of credit for that, more than the guys that coach me, because, once I get on the court, they can help me improve and get better. But if my body's not right, then they can't make any difference.

"When I went over to Miami, Mark Bender, the physio, was away from his family at Christmas. Not many people want to do that. Also New Year. He deserves a lot of credit for getting me back on the court and able to compete here."

Murray will be a hot favourite to go at least one round further given he next meets 119th-ranked Frenchman Stephane Robert, who won the battle of the lucky losers against Martin Klizan.