Andy Murray beats Ryan Harrison at Australian Open

Murray is the only Briton remaining in the singles at the Australian Open

Andy Murray had to battle past American teenager Ryan Harrison to book his place in the second round of the Australian Open.

The Briton started sluggishly, tamely losing the opening set before prevailing 4-6 6-3 6-4 6-2.

"I had a few nerves early on," said Murray. "I started to play better towards the end."

He will meet Frenchman Edouard Roger-Vasselin, who beat Belgian Xavier Malisse, on Thursday.

Fourth seed Murray, playing a major tournament under the watchful eye of new coach Ivan Lendl for the first time, will hope to improve on his opening-round performance.

Harrison, regarded as one of the game's up-and-coming talents, caused Murray major problems early on as he broke in the fifth game and eventually took the opening set in 51 minutes.

Murray broke early in the second set and was comfortable thereafter, wrapping up victory in three hours and 12 minutes.

He admitted he had to "dig deep" at the start of the second set.

"He [Harrison] came out playing great tennis, going for his shots and hitting big," said the Scot after a gruelling encounter in sweltering conditions on Hisense Arena.

"This court is tough - there's very little shade. We had a few long rallies and he made me do a lot of running. He is very good already and he's getting better.

"I'll need to make sure in my next match that I play closer to the baseline.

"You want to play your best tennis towards the end of the tournament so that's what I'll try and do."

There were few outbursts from Murray towards his support team during his early struggles, perhaps due to the presence of eight-time major winner Ivan Lendl, who is now acting as the Scot's coach.

According to Murray, Lendl was happy with the result.

Murray said: "He understands how you might be feeling at the start of a Grand Slam, what it's like to play against someone that you haven't played against, what it's like playing in different conditions and how you feel in really warm conditions.

"It's just good to have someone there that understands all of those things."

The 24-year-old added: "Someone maybe without the experience might walk in and be like, 'What the hell were you doing in the first set? What were you playing at in the first six or seven games?'

"He understands the feelings that you go through. Once I started moving better, I played better and the last few sets were good."

Murray improved considerably from the second set onwards, breaking Harrison after an energy-sapping fourth game and serving out confidently.

The momentum remained with Britain's sole remaining player in the singles draw and he earned two break points in the opening game of the third set, ruthlessly taking his first break chance when Harrison fumbled at the net.

A Murray victory seemed inevitable and he swiftly established a 3-1 lead in the fourth before breaking again for 5-2 and serving out.