By Alison Williams

LONDON (Reuters) - It would be hard to bet against the Williams sisters meeting in their first Wimbledon final since 2009, but Angelique Kerber and Elena Vesnina won't just be making up the numbers in the last four on Thursday.

While unseeded Vesnina has described her semi-final against world number one Serena Williams as a dream, she is playing inspired tennis, bringing the guile from two doubles slams to deliver baseline power and a deft touch at the net.

Fourth seed Kerber, meanwhile, has a 3-2 head-to-head lead over five-time champion Venus Williams and stunned younger sister Serena, who has won Wimbledon six times, at the Australian Open in January to win her first major final.

All four will bring a wealth of experience to Centre Court -- their average age is 31 years and nine months, the oldest for the last four in an open era women's major.

"The experienced players are ready to keep winning. They want to keep being great," Serena, 34, told reporters after she ground down 21st seed Anastasia Pavlyuchenkova in the quarter-finals.

She is aiming to equal Steffi Graf's open era record of 22 majors by lifting the trophy on Saturday, having been stuck on 21 since last year's Wimbledon. Of the challenge from her 29-year-old Russian opponent, she said: "I'll be ready for it."

Vesnina said of Serena after reaching her first major semi-final: "You have to give all your heart and fight for every single point and just use your chances because it is really difficult to break her, especially here on grass."

Like everlasting opponents on the other side of the net, Vesnina will also be taking on the American sisters in the doubles quarter-finals with her partner Ekaterina Makarova.

Venus, 36, has reached her ninth Wimbledon semi-final and owns seven slam titles overall -- the last coming on the grass in 2008, inevitably against her sister, before the result was reversed the following year.

It is nonetheless the first semi-final since the 2010 U.S. Open for the oldest woman in the 2016 Wimbledon field.

"Semi-finals feels good. But it doesn't feel foreign at all, let's put it that way," she told reporters after brushing past Kazakhstan's Yaroslava Shvedova in straight sets.

"All those other semi-finals helped me to have the experience to be in this semi-final."

Her perfect last-four record at Wimbledon could come under pressure though from Kerber, 28, who is trying to replicate the focus and relaxation that brought her the title in Melbourne.

The last player to win both the Australian and Wimbledon in the same year was Serena Williams in 2015 - the last German was Graf in 1989.

First up though is Venus. "She's always dangerous on grass, especially here in Wimbledon. She has a lot of confidence right now. She played great matches," Kerber said after beating Romanian fifth seed Simona Halep.

And it is Kerber who may have the last laugh: "I'm playing really good tennis right now. Yeah, I think I'm playing like in Australia, like really high‑class tennis."

(Reporting by Alison Williams; editing by Martyn Herman)