Andy Murray knows he will need to find his best form to progress further in the Australian Open with Roger Federer waiting in the quarter-finals.
Federer put in a vintage display to beat Jo-Wilfried Tsonga in straight sets on Monday, while Murray had rather more trouble seeing off another Frenchman.
Stephane Robert was the first lucky loser ever to reach the fourth round at Melbourne Park but for two sets it looked like his luck had run out.
Murray was asserting his authority against a player ranked 119 in the world and although the third set was closer, it would have been a routine win had the fourth seed taken one of two match points he held at 5-4.
But he double-faulted on the first, Robert saved the second and the 33-year-old took the set on a tie-break after two more match points had escaped Murray's grasp.
Murray eventually clinched a 6-1 6-2 6-7 (6/8) 6-2 victory on his sixth chance after a comfortable fourth set, but his struggles getting over the line certainly took the shine off a 12th straight quarter-final in grand slams he has contested.
Murray said: "He wasn't an easy guy to play against. The whole match was tricky. Obviously the end of the third set was tough mentally.
"I dominated 95 per cent of the match, and for 15 minutes I didn't close the match out. I was one point away from being in here after a great performance.
"But I still created chances, even when I wasn't playing so well at the end of that third set, and then the fourth set was fairly comfortable. I lost my serve once. So it was pretty good for the most part."
Murray and Federer last met in the semi-finals here 12 months ago, the Scot winning a five-set tussle before losing the final to Novak Djokovic
He leads the overall head-to-head 11-9 but that is the only one of their four grand slam meetings that Murray has won.
The 26-year-old came into the tournament having played only two competitive matches since back surgery last September and unsure how he would fare.
He has cleared every hurdle so far, dropping just the one set, but he knows the next test will be on a completely different level.
"It's a big match for me," said Murray. "It's the quarter-finals of a slam. Roger's played great tennis here in the past. It will be a very tough match for me.
"I said at the start of the tournament, I can't honestly say my expectations are as high as if I'd been playing for the last four months. It's been a good effort so far to get to the quarter-finals of a slam this soon after back surgery.
"So I'm happy with that. But I'm not far away from winning the event. Anyone that's in the quarters is close. I just look forward to that match and hopefully I'll play a good one."
Murray let his frustration show after dropping the third set by breaking his racquet - he later gave it to a fan as a souvenir.
The fourth seed is not one of the tour's regular racquet smashers, but he said: "Sometimes it's necessary.
"I had match points. I put a lot of hard work into that third set. I maybe lost concentration when I served for it. In the tie-break I didn't lose concentration, I just missed a couple of shots.
"Then losing that set was frustrating because it obviously means you're out there another 30 or 40 minutes at least, when I would preferably have been in the locker room.
"My racquet bit the dust, unfortunate for it. But I was glad I managed to start well in the fourth.
"It's not something as a player you're particularly proud of. But sometimes you just need to get some frustration out. I wanted to do it at that moment. I took my warning and moved on."
Robert was playing in the fourth round of a grand slam for the first time, and the quirky Frenchman made sure he soaked it all in, lapping up a standing ovation from the crowd on Hisense Arena.
He said: "They started shouting, 'Robert, Robert'. It's unbelievable for me. I'm happy. People enjoyed seeing my game today. It was a great, great feeling for sure."