Now, Murray bites the dust
Britain's Murray lost focus as he served for the match in the second set and was then battered by the hard hitting Janowicz, who ended the contest with a forehand winner and collapsed in joy.
"He probably gained some confidence from that (match point saved) and started playing better," Murray told a news conference. 'He (Janowicz) played a good tiebreak, played aggressive, he hits a very flat ball, so when he's hitting it well it comes through the court a lot,’’ he added.
The world number three's defeat means that for the first time since the 2010 Paris Masters was won by Swede Robin Soderling, a Masters title will be claimed by a player outside of the Big Four.
As another energy-sapping season draws to an end, world number four Rafael Nadal and Roger Federer opted not to play in the French capital while Serb Novak Djokovic was dumped out of the tournament by American Sam Querrey in the second round on Wednesday.
Argentine seventh seed Juan Martin del Potro will also have a few extra days to prepare for next week's ATP World Tour Finals at the O2 in London as he was beaten 6-4, 6-3 by local favourite Michael Llodra.
Spain's David Ferrer, the fourth seed, was the highest ranked player left in the draw after his 6-2, 4-6, 6-2 win over Swiss 16th seed Stanislas Wawrinka.
Frenchman Jo-Wilfried Tsonga will also travel to London next week after securing his spot with a 7-6, 7-6 win over Spain's Nicolas Almagro.
With Almagro out of the picture, Janko Tipsarevic completed the World Tour finals' line-up thanks to his 6-3, 3-6, 6-3 defeat of Argentine Juan Monaco. Janowicz will next face the eighth-seeded Tipsarevic. The 21-year-old Pole had not faced a break point in his first two Paris matches. But that run was unlikely to stay intact against a Grand Slam champion and he fell 15-40 behind in the 11th game.
The world no 69 saw off the first break point by following a big first serve at the net, only to double fault on the second.
Murray, who mixed his game with drop shots to break Janowicz's rhythm, claimed the set when his opponent sent a forehand long.
The Pole refused to give up but in the seventh game of the second set, a sizzling Murray return gave the Scot a break.
Murray lost focus when serving for the match, however, netting a routine forehand on match point, and dropped serve when he sent a backhand wide as the set went into a tiebreak.
Janowicz levelled the contest with a jaw-dropping dropshot on set point, and quickly opened a 4-1 lead as Murray, who had showed signs of nerves in the second set, failed to regain his composure.
Czech Tomas Berdych, the fifth seed, recovered from a terrible start to down South African Kevin Anderson 1-6, 6-3, 6-4.