France's Gilles Simon closed in on a place at the season-ending Masters Cup by beating Russian Igor Andreev 6-3, 7-5 in the second round of the Paris Masters on Wednesday.
Simon, eighth in the ATP Race after reaching this month's Madrid Masters final, will secure one of the three remaining tickets to Shanghai if his closest rivals do not reach the final at the Paris indoor event.
Spain's world number one Rafael Nadal, Swiss second seed Roger Federer, world number four Andy Murray of Britain and sixth seed Nikolay Davydenko of Russia, four of the five already in the Masters Cup, also reached the third round.
Top seed Nadal beat France's Florent Serra 6-2, 6-4, while Federer subdued Swede Robin Soderling 6-4, 7-6.
Murray, who won the Madrid Masters and retained his St Petersburg Open title earlier this month, extended his winning streak to 13 with a clinical 6-2, 6-4 win over American Sam Querrey.
Davydenko was made to sweat before he overcame big-serving Ljubicic 7-6, 7-5.
The 10th-seeded Simon would have been wary of Andreev since the Russian had come within a point of winning their first-round clash at the Madrid Masters just two weeks ago.
But having squandered four match points in their last meeting, Andreev again allowed Simon to stage a comeback and set up a third-round showdown with seventh seed Andy Roddick.
Simon trailed 3-1 before benefitting from a string of unforced errors to win five games in a row and claim the opening set and rallied from 4-0 down in the second to snatch victory on his second match point.
"I knew that if I was able to pass that round today I would be in a good position to go to the Masters. That was my main goal," Simon told reporters.
"As soon as I was able to go forward, I felt that I was a lot better than he was.
"I think it was very difficult for him when I was hitting my forehand to make winners. He's not used to having the ball come back when he plays those forehands, so he can become very impatient and make many unforced errors with his forehand."
Simon's victory means Argentine David Nalbandian, who beat German Nicolas Kiefer 7-6, 6-3, must retain his Paris title to book a trip to China.
He next faces compatriot and Davis Cup team mate Juan Martin Del Potro, who is seventh in the ATP Race and could lose and still book take one of the spots left up for grabs.
After an early exchange of breaks, Nalbandian and Kiefer held serve until the tiebreak which the eighth-seeded Argentine took 7-5 after 80 minutes after his opponent served a couple of double faults.
Nalbandian then broke in the second game of the second set to open a 3-0 lead, held serve and wrapped up the victory on his third match point.
"It's going to be a tough one (against Del Potro). We both know each other very well. We are in the Davis Cup team so we practice a lot," said Nalbandian, who beat Del Potro in the semi-final of the Swiss Indoors last weekend.
France's Jo-Wilfried Tsonga also kept his hopes of travelling to Shanghai alive when the number 13 seed claimed a 3-6, 6-4, 6-4 win over Czech Radek Stepanek.
The Australian Open finalist was at first surprised by Stepanek's cunning shots but he finally outpowered his opponent to set up a third-round meeting with world number three Novak Djokovic, who beat him in Melbourne in January.
Spain's David Ferrer, ninth in the ATP Race, and Swiss Stanislas Wawrinka, 12th, will not qualify for the Masters Cup after losing to German Philipp Kohlschreiber and Czech Tomas Berdych.
Kohlschreiber next takes on 11th seeded American James Blake, who still hopes to join the eight-man tournament after a 6-7, 6-3, 6-4 win over Italy's Simone Bolelli.