Novak Djokovic and Andy Murray started with contrasting victories at the Paris Masters on Wednesday, while Dominic Thiem's quest to qualify for the ATP World Tour Finals suffered a setback when he was knocked out.
Djokovic is in danger of losing his world number one status to Murray this week, but the defending champion had no trouble fending off the unseeded Gilles Muller 6-3 6-4 in just an hour and 20 minutes.
The top seed, winner of this tournament in each of the last three years and four times in total, saved the only break point he faced and needed just a break in each set to earn a meeting with Grigor Dimitrov.
Murray, on the other hand, had to show plenty of resilience to get the better of Fernando Verdasco 6-3 6-7 (5-7) 7-5 in the French capital.
Verdasco had the second seed on the ropes when he had two break points in the final set for a 6-5 lead, but the Brit hung in there for a huge hold and broke to love in the next game to ensure he will face Lucas Pouille in the last 16.
London hopefuls Marin Cilic and David Goffin will meet in the third round after seeing off Ivo Karlovic and Nicolas Mahut respectively, but Thiem's bid to qualify suffered a setback when he lost to Jack Sock, while Kei Nishikori claimed a landmark 300th tour-level win at the expense of Viktor Troicki.
DJOKOVIC PLAYS DOWN RANKING TALK
Twelve-time major winner Djokovic said he is more interested in rediscovering top form than concerning himself with the threat of being dislodged by Murray as he targets yet another triumph in this tournament.
"My attention is on playing match after match and putting quality and value into my game," said the Serb, who is guaranteed to keep top spot if he reaches the final.
"I know that if that's the case, then I can challenge anybody in the world on any surface and in any conditions. I'm quite pleased with the way things went on the court today. That's all I'm going to focus on."
Asked about the challenge of facing Dimitrov, he said: "I think Grigor is obviously a very talented player. He's been on the tour for some years now and he's more experienced. He has a good work ethic and is always trying to improve his game. He can hurt anybody with his big serve and forehand. I'm sure he's going to be very motivated to play well tomorrow."
VERDASCO PUSHES MURRAY ALL THE WAY
Murray was expected to make light work of Verdasco given his outstanding form and the Scot's record of 11 wins and just one defeat before they met for a 13th time.
But Verdasco served up a major challenge for a player who has won his last three tournaments, bossing many of the longer rallies and unleashing some classy winners to put Murray in danger of making a sharp exit.
Murray needed all the battling qualities which have brought him seven titles this year, hanging in there to put the world number 46 away in a contest which swung one way and the other before coming to an end after almost two and a half hours.
LONDON SETBACK FOR THIEM, WAWRINKA OUT
Two places are still up for grabs in the season-ending World Tour Finals, but Thiem will not be packing his bags for London just yet following his 6-2 6-4 defeat at the hands of Sock.
The Austrian, currently eighth in the ATP Race to London, could now slip below Cilic and Tomas Berdych this week.
Goffin and Jo-Wilfried Tsonga, a straight-sets winner against Albert Ramos-Vinolas on Wednesday, are also in the hunt to qualify.
Eighth seed Goffin ousted Mahut 7-6 (7-5) 6-3, with Cilic a 7-6 (9-7) 6-2 winner over Karlovic in an all-Croatian encounter.
Swiss third seed Wawrinka was eliminated, going down to Jan-Lennard Struff 3-6 7-6 (8-6) 7-6 (7-1).