Rafael Nadal battled to a 6-3 6-7 (5-7) 6-3 victory over a determined Pablo Cuevas to reach the Paris Masters quarter-finals on Thursday.
Nadal clinched the year-end number-one ranking with his second-round win against Chung Hyeon on Wednesday but he was put through the wringer at times by the Uruguayan in French capital.
Struggles on the Cuevas serve and a failure to take chances when they arrived made this a far more difficult match for Nadal than it needed to be, but it is the Spaniard who goes on to face qualifier Filip Krajinovic in the last eight.
Nadal was also made to work hard by Chung in the early stages of their encounter and he initially appeared intent on avoiding a similar scenario against Cuevas.
The Spaniard won the first game to love before converting his fourth break point to go 3-1 ahead.
Cuevas - undeterred by that break - produced a delightful 'tweener' to win the opening point of the fifth game on Nadal's serve and, while he was unable follow up his scene-stealing trick shot by restoring parity, the 31-year-old won his next two service games to love as he settled into the match.
And Nadal made hard work of wrapping up the set, needing four set points to move in front having led 40-0.
After taking only one point from Cuevas' previous three service games, Nadal built up a head of steam on his own serve early in the second set before breaking to go 2-1 up.
But Nadal could not make it stick, sending a forehand wide to bring Cuevas level, and he soon slipped back to struggling on his opponents' serve.
He lasted to a tie-break but sent a backhand long to hand Cuevas the set, receiving treatment on his right knee before the decider commenced.
Nadal's period with the trainer appeared to revive him briefly as he opened up a 3-0 lead and, when Cuevas cancelled out that break advantage in the fifth game, the world number one hit back immediately.
Cuevas' long forehand that handed the initiative back to Nadal seemed likely to be the decisive blow to his chances of causing an upset and so it proved - a relieved Nadal put the match to bed after two hours and 20 minutes on court.