ANDY MURRAY was relieved to put the challenge of giant Croatian Ivo Karlovic behind him to reach his eighth consecutive quarter-final here.

The Scot beat Karlovic 7-6, 6-4, 5-7, 6-4 in three hours and three minutes on Centre Court, and will now meet the unseeded Vasek Pospisil in the last eight.

Pospisil, from Canada, defeated the Serbian No.22 seed, Viktor Troicki, in five sets.

Karlovic is 6ft 11in – the tallest man ever to have played on the ATP tour and one of the hardest servers – but Murray is the best returner in the game, and varied his play well, often lobbing his opponent when he had come into the net.

“I returned his second serve well and I passed well,” Murray said after the fourth-round match.

“Against him, it’s a tactical match, but it’s tough. It’s quite stressful to play against him.

“I was expecting nothing different to what I got today. I expected it to be a very difficult match. I expected a lot of the sets to come down to one or two points, and that was the case.

“I’m happy that I got that match under my belt, managed to win it, because it could easily have gone the other way. Often he comes out on top in matches like that.”

Murray had won all five of his previous meetings with Karlovic, only ever losing a set on a tie-break. The first 10 games all went with serve, although Karlovic had to save a set point in the last of them. Serving again at 6-5 down, he saved three set points with a series of magnificent serves, forcing the set into a tie-break.

He saved two more in that, too, before eventually losing the breaker 9-7.

The No.3 seed pressed home his advantage at the start of the second, breaking Karlovic immediately.

The older man recovered well from that shaky start, but had to save two more break points at 2-4.

At 4-5 behind, he served successfully to stay in the set, but then could do nothing to stop Murray taking it in the next game.

So far so straightforward for Murray, but Karlovic hit back in the third.

He served better, he cut down on the error count that had cost him dear in the first two sets, and he got his reward when he broke Murray with his first set point.

Encouraged by that improvement, the 36-year-old looked increasingly confident as the fourth set began, and in many rallies had Murray on the back foot.

But it was the Scot who had the first break point of the set, in the seventh game, and he got it – although only after he had successfully challenged a ruling that his opponent’s shot down the line was in.

Murray had to save two break points himself in the next game before taking it to go 5-3 ahead.

Karlovic bravely saved a match point in the following game, but could do nothing to prevent Murray from serving out for the match and clinching tomorrow’s meeting with the unseeded Pospisil.

Murray has played Pospisil three times in the past year, but always on hard court.

The Canadian may be feeling more than a little tired when the two meet, because as well as going the distance against Troicki, he and doubles partner Jack Sock later played five sets against Jamie Murray and John Peers, losing in the end.

“I’ve never played him on grass,” Murray said of Pospisil. “He’s had a good run here. Obviously won the doubles here last year. Can play well on the surface.

“He’s also played a lot of tennis here, which is a positive for him in some ways.

“But also maybe he’s a little bit fatigued. So if that is the case – and I won’t bank on that being the case – but if that is the case, I’ll try to use that to my advantage.

“Although my match was quite long, the rallies aren’t particularly long, and it’s not as physical. So I feel pretty fresh.”

Defending champion Novak Djokovic fought back from two sets down to level his match against Kevin Anderson before bad light stopped play.

The world No.1 and top seed looked in trouble on Court One as the big-serving South African took the first two sets of the fourth-round tie. But Djokovic fought back to level 6-7 (8-6), 6-7 (8-6), 6-1, 6-4 after three hours and four minutes.

Djokovic was keen to play on but must return to try to complete his comeback on the same court at 1pm today.

Seven-time champion Roger Federer reached the quarter-finals for the 13th time by dismantling Roberto Bautista Agut.

Second seed Federer was close to his imperious best, employing his full range of shots as he won 6-2, 6-2, 6-3.

The Swiss will next face Gilles Simon for a place in the semi-finals. He needs one more title to break the record he holds with Pete Sampras and Willie Renshaw. “I don’t think I made a statement,” said Federer.

“I did a nice job making the transition. It was a good match. I got off to a good start and kept rolling. Obviously maybe Roberto wasn’t at his very best.”

STan Wawrinka made the last eight for a second consecutive year by beating David Goffin.

The Swiss fourth seed and French Open champion won 7-6 (7-3), 7-6 (9-7), 6-4 to set up a last-eight tie with Richard Gasquet, who beat Nick Kyrgios in a dramatic match.

The Australian showman denied that that he stopped trying after he appeared to give up for a game early in the second set of his 7-5, 6-1, 6-7 (7/9), 7-6 (8/6) loss, and could face punishment from the International Tennis Federation.

He also sparred with the umpire over switching his socks at the first changeover in the third set.

The umpire looked to think he was taking too long, with Kyrgios saying: “If you’re going to get angry with me for that, that’s another level. All I’m doing is putting my sock back on.”

In what looked to most impartial observers to be an act of immature rebellion, Kyrgios let two serves slide by him for aces without even swinging his racquet. He meekly fed back two further Gasquet serves into the net.

But he rejected the theory that he was not giving it his best effort. He said: “I kept playing. He hit a serve past me as an ace. That’s too good. If they decide to fine me, they can fine me.