Heavyweights Novak Djokovic and Rafael Nadal have rolled into the third round at Wimbledon, but last-year’s runner up Marin Cilic has been knocked out of the grand slam in an upset loss.

Novak Djokovic overcame an apparent thigh problem to beat Argentine Horacio Zeballos 6-1 6-2 6-3 on Thursday.

Djokovic called for a trainer and had his left leg massaged when leading 4-3 in the third set.

But he easily held serve in the next game and broke Zeballos again to close out the match.

However, Cilic, a favourite to go far in the tournament again this year, suffered a shock 3-6 1-6 6-4 7-6(3) 7-5 defeat by Argentine Guido Pella.

The Croatian third seed began the day two sets up but 4-3 down on Pella’s serve in the third, following Wednesday evening’s halt for rain and found his opponent very much up for the fight.

Pella wrapped up the third set comfortably, then shaded an exciting fourth set that included two breaks of serve for each player with Pella taking command in the tiebreak to clinch it 7-3.

The deciding set went with serve until Pella clinched his first victory over a top-five player on his fourth match point after Cilic had already saved two in the 10th game and another when 30-40 down.

Pella, who has very limited experience on grass and had lost to Cilic in three sets at the 2015 U.S. Open in their only previous meeting, was undoubtedly helped by Wednesday’s rain interruptions.

Meanwhile, top-ranked Nadal laboured into the third round with a tricky 6-4 6-3 6-4 win over Mikhail Kukushkin of Kazakhstan on Centre Court.

The Spaniard won only 64 per cent of points on his first serve and faced 13 break points – including three in the first game of the match – but he saved 11 of them and converted five of his own to wrap up the win in two hours and 23 minutes on Centre Court.

The 11-time French Open champion is looking for his third title at the All England Club and first since 2010.