Wimbledon 2015: Andy Murray holds his nerve in the face of Ivo Karlovic's big serve
Andy Murray furthered his reputation as one of the sharpest returners in the game as the Scot overcame Ivo Karlovic's demon serve to book his place in the Wimbledon quarter-finals.
Karlovic's 136 aces put him top of the tournament leaderboard at the start of play but, while the 6ft 11in Croatian added another 29 to his tally, precision won over power as Murray sealed a 7-6 (9/7) 6-4 5-7 6-4 victory.
"It was an incredibly difficult match," Murray said.
"It was tiring, it's not so physically difficult because the points are quick but it's mentally tiring and you have to ready when the chance comes."
A place in the semi-finals now rests on Murray beating Canada's Vasek Pospisil, who knocked out Britain's James Ward in round three.
Murray had never lost to Karlovic in five past meetings, but the world number 25, who takes a size 16 shoe, knocked out two-time Wimbledon semi-finalist Jo-Wilfried Tsonga in round three and remains a daunting opponent on grass.
The statistics pointed to a clash of serve versus return with Karlovic enjoying the highest percentage of first-serve points won in the tournament, while Murray boasted the highest percentage of return games won and the most points taken against opponents' first serve.
The British number one predicted his opportunities to crack Karlovic would be few and far between, but a break point arrived in the very first game as Murray looked to catch his opponent cold.
The chance went begging, however, and Karlovic, to a chorus of gasps and whistles from the Wimbledon crowd, made his mark with two aces and a 134mph rocket.
Between the Croatian's one-shot whoppers, one of which clocked a helpless line judge on the head, Murray was able to dictate the rallies and the Scot was frustrated by almost any point he lost which lasted longer than two shots.
Three more break point opportunities came just at the right time for Murray as he led 5-4 and then 6-5, but on each occasion Karlovic served his way out of trouble to force the tie-break.
The Croatian assumed a commanding position when he pulled 4-2 clear, but Murray came storming back and, after 57 minutes, converted his seventh set point at 8-7 when a Karlovic forehand flew long. Buoyed by his advantage, Murray began to loosen up and some brilliant returning gave him an instant break in the second set as Karlovic began to flounder in the face of his opponent's subtle shot-making.
Two more break points came and went for Murray in the seventh game, but Karlovic rarely threatened and the Scot served out to love to clinch the second set.
The 36-year-old refused to lie down, however, and his chip and charge tactics kept the pressure on Murray, who was forced to serve for a tie-break in the third as he trailed 6-5.
A broken string from a first serve created a delay in play at 30-30 and Karlovic pounced to seal the set 7-5 as Murray hit a sloppy backhand into the net.
Centre Court fell flat at the prospect of another set of boom-and-bust, but Murray maintained his composure and in the seventh game seized the decisive break.
The Briton did brilliantly to retrieve another thundering Karlovic serve, but the Croatian's winning volley looked to have caught the line before, to the surprise of both players, an optimistic challenge fell in Murray's favour.
Karlovic dug deep to hold one more time but he could not prevent his opponent serving out as Murray sailed through to his 18th consecutive grand slam quarter-final.