Pioline's win keeps the Frenchman on course for the end of season finale and maintained the hopes of Boris Becker, who also reached the semi-final, of defending his world title.
Pioline's chances of reaching the finals now depend on Becker. If the two reach Sunday's final, then the Frenchman must win to get a place.
Meanwhile, Becker gained revenge for his defeat in the fourth round of the US Open when he beat Sweden's Magnus Larsson 6-1, 7-6.
Becker will face Magnus Gustafsson in the semi-finals after the Swede beat Becker's German compatriot, Michael Stich, 7-6, 7-5.
Becker is still seeded seventh in the world but unless he wins this tournament he is expected to tumble well out of the top eight. Seven of the eight places have already been taken, by Pete Sampras, Jim Courier, Sergi Bruguera, Stich, Stefan Edberg, Andrei Medvedev and Michael Chang.
Becker has not won an event since the spring but yesterday he found some of his old form against Larsson. He was totally on top in the first set, displaying some of the aggressive all-court game that made him the world No 1 only two years ago. Serving well, and playing near-flawless groundstrokes, he wrapped up the first set in just 23 minutes.
But this year Becker has never been able to sustain his form, and he was quickly trailing 5-2 in the second set. He started complaining, as usual, swinging at thin air and shouting, mostly at himself.
Unlike his earlier matches, though, it immediately paid off and he steadily fought himself back into the match. In the previous rounds of the tournament he wasted almost any break point thrown at him, but yesterday he used the first to get back in the match and force a tie-breaker. 'This time, I was able to capitalise on the opportunities,' he said.
Larsson, ranked 39th in the world, collapsed under the pressure, and did not win a single point in the tie-break.
Clare Wood will spearhead Britain's defence of the European Women's Team Championship in Sheffield from 24-28 November.
The Sussex player, who won her second Volkswagen National title at Telford last week, is joined in Ann Jones's squad by two teenagers, Mandy Wainwright of Essex and Shirli-Ann Siddall of Dorset, and by fellow 25-year-old Valda Lake of Devon.
Britain won the event for the first time in Prague last year, led by Jo Durie, who is unavailable this time because of a knee injury. Wood and Siddall were also in that team.Reuse content