(adds Bartoli retirement)
By Mark Ledsom
ZURICH, Oct 19 (Reuters) - World number one Justine Henin brushed aside Polish teenager Agnieszka Radwanska 6-4 6-2 in the quarter-finals of the Zurich Open on Friday to maintain her incredible run this year.
Henin has reached the semi-finals of all 13 tournaments she has participated in, winning eight trophies.
"The last time I wasn't in a semi-final was in Miami in (April) 2006 so that's a pretty long time," the Belgian told reporters.
"But I'm not playing for records. I'm just loving my tennis."
Henin's chances of winning her ninth title of the season were boosted further on Friday by the retirement through injury of second-seeded Russian Svetlana Kuznetsova and French ninth seed Marion Bartoli.
Their withdrawals left the Belgian as the only seed still involved in the event.
"There was a bit of frustration in the first set because I couldn't get a good rhythm," said Henin after securing her 17th successive win on the tour.
"She was serving pretty slow so it was tough for me to come in and play aggressive. But in the second set it was like the machine just switched on."
Kuznetsova and Bartoli became the latest casualties of a tournament that has seen four top players retire hurt.
World number two Kuznetsova pulled out of her meeting with Italy's Francesca Schiavone with a shoulder injury while trailing 3-6 3-3.
Bartoli then left the court in tears after abandoning her match against compatriot Tatiana Golovin, immediately after breaking to take a 5-4 lead with serve in the first set.
Organisers said the ninth seed had injured her left knee, apparently while overstretching on her forehand, and would see a doctor on Saturday.
Kuznetsova said her own injury would not jeopardise her place in next month's season-ending WTA championships.
"It's not that serious, I just need some time off because the muscle was getting very tired and I couldn't lift my arm up," Kuznetsova told reporters.
"In the second set I could get it together but I was thinking, 'What's the point?'. If I had won the second set I wouldn't have been able to finish the match."
Henin next plays Czech world number 15 Nicole Vaidisova, who defeated Ukraine's Alona Bondarenko 6-1 6-4.
Schiavone and Golovin, the direct beneficiaries of Friday's two retirements, meet in Saturday's second semi-final.