Andy Murray survived a shoulder injury scare to make the Wimbledon last 16 with a 6-2, 6-2, 1-6, 6-1 win over Italy's Andreas Seppi.

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Murray, the 2013 Wimbledon champion, required a medical time-out for treatment on his right shoulder after dropping the first game of the fourth set. But the world number three then reeled off six games in succession to set up a clash against Croatian giant Ivo Karlovic for a place in the quarter-finals.

Third seed Murray raced through the first two sets before 31-year-old Seppi called for treatment on his right ankle. It worked wonders for the 25th seed, who captured the third set and was a break to the good in the fourth.

But Murray was revived by his shoulder treatment and swept through the remaining six games, taking victory on his 10th ace, having also hit 32 winners.

"The shoulder is fine. You probably saw towards the end of the second set it tightened up next to the shoulder blade," said Murray. "The trainer came out and manipulated my back. He gave it a few good cracks.

"It's a 90 kilo guy lying on top of me so it's not that pleasant." He added: "The way I finished the match is how I want to play the rest of the way."

Murray will take a 5-0 career record into his with 36-year-old Karlovic, who has hit an intimidating 136 aces in three rounds so far.

"It will be a very different match from today. Ivo is going to be coming to the net a lot," said Murray. "He's served very well so my returns will have to be on if I want to get through that one."

Karlovic became the oldest man in 39 years to reach the last 16 when he beat French 13th seed Jo-Wilfried Tsonga. The 36-year-old giant fired 41 aces in a 7-6 (7/3), 4-6, 7-6 (7/2), 7-6 (11/9) win.

Elsewhere, 2010 runner-up Tomas Berdych, the Czech sixth seed, saw off Spain's Pablo Andujar 4-6, 6-0, 6-3, 7-6 (7/3). He next faces either Gilles Simon or Gael Monfils.

Seven-time champion Roger Federer defeated big-serving Australian Sam Groth 6-4, 6-4, 6-7 (5/7), 6-2. The 33-year-old Swiss, chasing an 18th major title, will next face Spanish 20th seed Roberto Bautista Agut.

US Open champion Marin Cilic took just two games to see off John Isner after returning to finish their third round match poised at 10-10 in the final set. He next faces wildcard Denis Kudla, the last American man in the tournament.

Viktor Troicki halted Dustin Brown's Wimbledon fairytale and goes on to face Canada's Vasek Pospisil, who beat British wildcard James Ward. 

It is the 29-year-old Serb's first last-16 run at Wimbledon since 2012 and his best performance at a Grand Slam since returning from a 12-month drugs ban in July last year.