Roger Federer made hard work of the start of his Masters Cup defence on Sunday before recovering to squeeze past Argentine David Nalbandian 6-3, 2-6, 6-4.
The runaway world number one is chasing a third consecutive finale title -- a feat last achieved by Ivan Lendl in 1985-87.
In Sunday's second Red Group match, Croatia's Ivan Ljubicic beat another Argentine, Guillermo Coria, 6-2, 6-3.
Monday's Gold Group matches will pit Andre Agassi against Nikolay Davydenko and Rafael Nadal against Gaston Gaudio.
Federer was playing his first match since being sidelined by an ankle injury after winning his 11th title of the season on Oct 2 and appeared rusty at stages.
He made an unusually high number of unforced errors against last-minute qualifier Nalbandian and found himself 3-1 down in the final set after a break of serve.
However a crunch backhand volley gave the Swiss a chance to claw his way back in the fifth game of the set at the state-of-the-art Qizhong Stadium and he never looked back.
"Thank God I got out of that one," the Wimbledon and U.S. Open champion said.
"I was mentally ready for a two-sets defeat...(but) I took the opportunity he gave me and I'm very happy right now."
Nalbandian -- who now leads Federer 5-4 in matches played having won the pair's first five meetings -- was less thrilled with his performance.
"I feel I didn't prepare a hundred percent for this Masters. I was already on holiday when I received a last-minute call to come here," he said.
"GREAT PLAYER"
"He (Federer) is a great, great player with a lot of confidence. When I took the break (in the third set) I knew it was a very important game and I tried to stay focused but it wasn't enough."
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The 1.93-metre Ljubicic, who was one of the last to qualify for the tournament, used his height advantage to punch his way to an emphatic victory.
He recorded six aces to the Argentine's one and frequently left his opponent standing as he executed lightning-quick volleys and smashes.
"My game had to be really physical in the sense of hitting hard. He (Coria) is fast, but he is not faster than the ball," said Ljubicic.
"I think I played a great match...everything went my way, especially in the first set."
In a late-season run of form, the Croatian number one reached the finals in four of his last five tournaments, taking victory in Metz and Vienna and ensuring his qualification for Shanghai.
Next up for him, however, is the daunting prospect of Federer.
"I don't think it's going to be the key match of the group, so I can relax," the Croatian said.
Ljubicic has met and lost to Federer in three 2005 finals, each time on a hard surface. "I don't think it's an advantage for me that I've played so many matches against him because he's going to be really careful how he faces this match. He knows that I can give him some trouble," he said.
