Safin, seeded third this year, lost to Thomas Johansson in the 2002 Australian Open final.
In the final match of the day in Shanghai, Thomas Johansson took part in the event for the first time.
Swede Thomas Johansson (16) became the first men's seed to taste defeat as he lost to Nicolas Lapentti of Ecuador.
Men's champ Roger Federer was one of the first players on court and he didn't hang around long against Thomas Johansson.
In Thursday's other third round matches, Thomas Johansson 's attempt to claim a place in the Masters Cup suffered an unexpected setback.
The day ended with an impressive performance from 18-year-old Argentine Juan Martin del Potro, who beat Swedish veteran Thomas Johansson 6-2 6-4.
Safin was hot favourite to win the Australian Open final in January but was beaten in four sets by 16th seed Thomas Johansson.
His success in 2002 stemmed from a surprise semi-final appearance at the year's first Grand Slam in Australia where he lost to eventual champion Thomas Johansson in a five-set thriller.
Mathieu, who had reached the quarter finals when Thomas Johansson retired with back spasms, is chasing his second career title after his victory in Moscow last week.
Instead, his game fell apart in the fourth round against journeyman Jonas Bjorkman and he crashed out in straight sets - allowing Thomas Johansson, a player no better than him, to come through and take the title.
Caroline Wozniacki held on to the top ranking for more than a year, but she's now No. 9 and searching for answers with a new coach, former Australian Open champion Thomas Johansson, who was hired in the past few weeks.
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