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 yesterday 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 yesterday 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 favour after Jankovic  committed the cardinal sin of failing to finish off a Williams  sister when the chance presented itself.  Venus, 29, is the first player to reach the final after  losing two matches in the round robin stage since Frenchwoman   Amelie Mauresmo in 2003.

“In the first set I couldn’t feel the ball and couldn’t seem  to get a ball in,” said Venus.