Novak Djokovic was given a stern test at the Rogers Cup in Toronto where he survived two tight sets to beat Luxembourg’s Gilles Muller.
Playing his first match since losing in the third round at Wimbledon, the world No 1 was on court for 104 minutes in posting a 7-5 7-6 (7-3) victory.
Djokovic needed two chances to wrap up the win, after he failed to serve out for the match in the 10th game of the second set, when he was broken to 15.
However, he recovered his composure in the tie-break which he took 7-3.
Muller, the 33-year-old world No 37, appeared to be staging a recovery towards the end of the second set but – from 3-1 up in the tie-break – he was powerless to prevent the Serbian from reeling off six straight points.
Djokovic, who suffered a shock defeat at SW19 earlier this month when he lost to Sam Querrey, will now face the experienced Radek Stepanek in the last 16.