ANDY Murray was grateful for an inspired Hawk-Eye challenge as he booked his place in his eighth successive Wimbledon quarter final, then thanked his brother Jamie for tiring out the opponent he will face when he gets there.

While the World No 3 was easily the superior player against Ivo Karlovic, the big-serving 6ft 11in World No 23 from Croatia, the crucial break in the fourth set of his 7-6 (7), 6-4, 5-7, 6-4 came only after video technology showed that a Karlovic volley landed 2mm into the tramlines. The Scot has a reputation for ill-judged Hawk-Eye challenges but getting that one right proved crucial.

With the unseeded Vasek Pospisil, of Canada, waiting in the next round, Murray's hopes of a second Wimbledon crown burn brighter than ever, not least because the 25-year-old Canadian spent a total of ten hours on court yesterday. After he battled back to claim a five-set victory against Viktor Troicki of Serbia, Pospisil then suffered a gruelling defeat with his doubles partner Jack Sock, 8-6 in the fifth to Jamie Murray and John Peers of Australia. World No 1 and favourite Novak Djokovic's berth in the last eight isn't secure yet either, with the Serb scheduled to resume tied at two sets all with giant South African Kevin Anderson, while Tomas Berdych and Nick Kyrgios were two of the day's other high profile fallers.

"I've been playing under Hawkeye for like 10 years now," said Murray. "I can't obviously remember all of the ones that have gone for me and against me. But that was obviously a very important one today. It won me the match."

Pospisil is an opponent against whom he has never lost, in three meetings, all of them coming on a hard court. Murray has no plan to let it happen on Wednesday. "He's had a good run here and obviously won the doubles here last year," Murray said. "So he can play well on the surface. He's also played a lot of tennis here, which, you know, is a positive for him in some ways. But maybe he's a little bit fatigued. So if that is the case, and I won't bank on that being the case, I'll try to use that to my advantage. Although my match was quite long today, the rallies weren't particularly long, and it's not as physical. So I feel pretty fresh."

His brother Jamie, who also booked his first Wimbledon quarter final in his preferred event, the men's doubles, agreed. "I think he [Pospisil] will be pretty tired, I hope he will be, because I am pretty tired and I did half as much as he did," said Jamie. "But it is his first Grand Slam quarter final and I am pretty sure he will be looking forward to it."

Murray showed little ill effects of the shoulder problem that had dogged him during his previous match against Andreas Seppi of Italy. While he deliberately took some pace off his first serve to maintain a higher percentage, he admitted the area is still heavily strapped. "Yeah, it feels better," said Murray. "I would have liked to have served a little bit bigger today, a little bit harder. That's something that as I go on in the tournament, I'll need to try to do more of. I am still conscious of it and am playing with quite a lot of taping on the shoulder. But obviously I played for three hours today and it feels better than it did three, four days ago, which is positive."

With Leon Smith, his first coach and Great Britain Davis Cup captain, set to announce his squad for the match with France today, Murray threw his weight behind the idea of allowing him to job share in a lead coaching and performance role within the Tennis Scotland structure. Talks with the LTA and the Scottish governing body are due to take place on that subject in the next few days.

"Obviously Leon, in most of the jobs he's done over the years, he's been successful," said Murray, on a day when two Scots, Anna Brogan and Maia Lumsden, knocked out the No 1 and No 3 seeds in the girls singles respectively. "He's obviously passionate about tennis in this country. He's done a great job as the Davis Cup captain. When he was based in London, or spending a lot of time in London, he was somewhat wasted a little bit in the offices and stuff. I think he's best, with what his skill set is, being on the court. His time would be best spent on the court with younger prospects, for sure."

As for his own prospects this fortnight, Murray is entitled to feel pretty good about his chances. "I'm happy that I got that match under my belt, and managed to win it, because it could easily have gone the other way," he said. "Often he [Karlovic] comes out on top in matches like that.

"I'm playing well," he added. "I'm through into the quarterfinals against Pospisil, which is a good opportunity for me. I don't know how to answer those questions about whether it's the best I've felt at the quarterfinal stage or not."