Novak Djokovic was spotted wearing an unusual pair of gloves between games during his Miami Open victory over Sebastian Korda. The veteran Serb was made to work hard for the win but found an extra gear to record a 6-3 7-6 triumph and book his place in the semi-finals, where he will face Grigor Dimitrov.

Djokovic made a flying start to proceedings, turning the screw in the opening set to draw first blood. He began to toil early in the second, though, with Korda securing an early break. The underdog was 5-2 up at one stage but Djokovic somehow battled back to force a tiebreak, which he won to ensure a straight-sets victory.

His impressive revival seemed to coincide with the adoption of a bizarre tactic during breaks in play. Djokovic was seen wearing large blue gloves, which he rubbed on his neck and face while sitting in his chair, and started to play better almost immediately.

It later transpired that Djokovic was cooling himself down with ice packs, which had been placed inside the gloves. Sky Sports pundit Martina Navratilova was impressed with the 37-year-old thinking outside the box to cope with the difficult conditions.

"They've had this years ago, it can lower your body temperature in like 30 seconds," said Navratilova. "It cools down the blood supply. I don't know why more people haven't been using them.

"Novak is ahead of everybody when it comes to technology. It's magic and I don't know why tournaments don't have them for all the players."

Djokovic was pleased with his battling performance against Korda, who looked almost certain to force a decisive third set but was powerless to prevent the Serb from turning the tide.

"I'm feeling very relieved that I won in straight sets, to be quite frank," said Djokovic in his post-match interview with Sky Sports.

"The highlight of the match for sure was my first serve. I've been sering really well and today was my best serving performance [of the Miami Open]. I was quite nervous because you never know what comes from Korda. He's so aggressive and so talented.

"I was on my back foot, so to say, and trying in some moments to passively wait for his error instead of trying to dictate the tempo from the baseline. I managed to break back and got myself in a winning position. Very tense match but a great performance."