DOHA (Reuters) — Holder Venus Williams completed her circuitous route to the WTA Championships final, beating Serbia’s Jelena Jankovic 5-7 6-3 6-4 on Saturday to set up yet another showdown with sister Serena.

Serena, who will end the year as world number one for the first time since 2002, got past Caroline Wozniacki after the Dane pulled out with a stomach injury when trailing 6-4 0-1.

“I wasn’t playing great. I think it’s hard to play well against a player who’s injured and is so nice,” Serena told reporters. “I’m going to have to really improve my game against Venus if I want to win.”

The Williams sisters have already met across the net in the Qatari capital this week, Serena winning a three-set scrap in their Maroon Group clash which was their 22nd career duel.

There will be no Williams clean sweep on Sunday though after they lost 2-6 6-4 10-8 in the doubles semi-final to Nuria Llagostera Vives and Maria Jose Martinez Sanchez.

The Spanish duo will face world number one pairing Cara Black of Zimbabwe and American Liezel Huber on Sunday.

Venus seemed down and out after defeat by her younger sister followed an opening group loss against Elena Dementieva.

After beating Svetlana Kuznetsova, though, some complicated maths edged her through to the last four by virtue of sets won.

It was all a bit unconvincing again on Saturday as the seven times grand slam champion sprayed errors around the court and also needed treatment on her knee several times.

Gradually she turned things in her favor after Jankovic committed the cardinal sin of failing to finish off a Williams sister when the chance presented itself.