Andy Murray had to come through a disturbing funk and a lot of drama to beat Andreas Seppi on the sixth evening of the 2015 championships, yet the character he showed in overcoming a third-set blip suggested he remains the biggest threat to Novak Djokovic’s title defence.

After two hours and eight minutes of enthralling tennis, Murray can come away from his 6-2, 6-2, 1-6, 6-1 win over the Italian relieved and happy with the way he handled what he appeared to regard as Seppi’s outrageous gamesmanship in the third set. At the end, they smiled and hugged at the net, after Murray had clinched the win with his 10th ace, but the atmosphere was not so friendly for a long stretch of the match.

It could have gone horribly wrong for the Scot when Seppi – who had beaten him only once in six attempts – went two sets down, and, leading 2-1 in the third, took a medical timeout for attention to his shin. He returned to the fray untroubled in his movement and won six games in a row over the next half-hour, breaking Murray twice to take the set.

Asked afterwards if he knew how Seppi’s leg was, Murray said: “I don’t know what his problem was … I was having a few issues with my serve. Then when he took the injury timeout, I came out and I was stiffer.”

Murray’s mood, buoyant in the first hour, changed dramatically. He received attention courtside on his right shoulder after being broken again at the start of the fourth. Was it retaliation for Seppi’s timely break? Nobody could be sure. Tennis has become a psychological as well as physical jungle and there are swamps at every turn.

Not for the first time, Murray seemed perturbed when his opponent wobbled physically, then came back hard at him to stop his momentum. But, unlike his losses to Djokovic in the final in Melbourne and the semi-final at Roland Garros, he drew inspiration from the interruption. He fist-pumped and cajoled himself into action, moving with urgency and purpose between points in the fourth set, impatient to get back into the game.

In the fourth set, Murray broke him almost at will, angry but focused, and served the match out in fading light to the delight of the packed arena.

Seppi, an accomplished 31-year-old from northern Italy and his country’s best player, had taken just two sets off Murray in seven matches, nine years ago on the grass of Nottingham. His slam form this year has fluctuated: he beat Federer in the third round in Melbourne (his first win in a major over a top-tenner) but John Isner took him out in straight sets in the first round at Roland Garros. Ever so briefly, though, he looked as if he might spring a significant upset.

Murray is into the second week of his home tournament for the ninth time in 10 visits. But it was a close-run thing.

Whatever his views on timeouts – and he was diplomatic afterwards, while stating that his was the first one he had taken this year – the Scot was confident his shoulder was not going to cause too many problems. “It’s something I had the last two, three days. And, yeah, I mean, I only really feel it when I’m serving. But it’s not something that’s of major concern to me.”

Looking down on Murray’s performance from the royal box on a warm and pleasant Saturday evening – alongside Gary Lineker and the England rugby union captain, Chris Robshaw – was Boris Becker, esteemed here as the youngest champion 30 years ago and now the mentor of the defending champion, Djokovic. He will have noted the ups and the downs.

Murray’s next obstacle, in the fourth round on Monday, is bigger in every way: the 6ft 10in Ivo Karlovic, who earlier on Saturday became the first player in the recorded history of the game to hit 40-plus aces in three consecutive matches and, at 36, seems only to be getting better.

Karlovic goes into the match with some hard miles on the clock, and surely the weariest right arm in the tournament. He took two hours and 50 minutes and three tie-breaks to beat the 13th seed, Jo-Wilfried Tsonga, 7-6 (7-3), 4-6, 7-6 (7-2), 7-6 (11-9) on No3 Court, adding 41 aces to the 53 he struck in beating Alexandr Dolgopolov and the 42 in the first round against the Swedish qualifier Elias Ymer.

But his extraordinarily long legs covered 1,924 metres against the artful Frenchman and he will start to properly feel the strain if Murray keeps him on the end of his nagging ground strokes.

The Croat took his tournament tally to 136 to stay well on top of the leaderboard for free points. Although he has not beaten Murray in five attempts and last played him here in 2012, he will be tough to beat.

“It will be a very different match from today,” Murray said. “Ivo will be coming to the net a lot. Returns are going to have to be on.”

Beyond Karlovic lies either Viktor Troicki, whom he tamed in the semi-finals at Queens, or Vasek Pospisil, the Canadian who took five sets to beat James Ward. If the form guide holds, Federer will be waiting for him in the semi-finals.

For now, Murray has time to rest and gauge the battle ahead. In a way, Seppi did him a favour. He turned on a switch to his elemental beast – and it roared with astonishing ferocity at the conclusion of a performance that will serve the world No3 well in harder assignments to come.