By Pravin Char

LONDON (Reuters) - When Serena Williams and Angelique Kerber walk onto Wimbledon's Center Court for the women's final on Saturday, the legacy of Steffi Graf will loom large.

The showdown will see world number one Williams try to equal Graf's professional era record of 22 grand slam singles titles, while Kerber will seek to become the first German woman to lift the Wimbledon singles crown since her idol Graf 20 years ago.

If Kerber prevails, completing a daunting double over the Williams sisters at the tournament, it could also signal a changing of the guard at the top the women's game.

It would be the second time this year she had beaten the American in a grand slam final, having triumphed at the Australian Open in January.

Kerber, 28, would also become the first woman apart from Williams to win two grand slams in a season since Justine Henin in 2007, when the Belgian player was world number one.

Williams, who turns 35 in September, is a six-times Wimbledon champion and the clear bookmakers' favorite. But the Graf milestone is nevertheless sure to be weighing on her mind.

She has flatly refused to discuss it at this year's championships, on one occasion testily telling reporters: "I'm not talking about that anymore. Sorry."

Kerber, free of such weight of expectation and history, has been happy to discuss her ambitions to emulate Graf.

"She was always an idol for me, I have watched a lot of her matches, on YouTube sometimes," she said after dispatching Williams' sister Venus in the last four. "I met her a few times -- the last time she told me, just believe in yourself.

"I will try to be the next one to win here after Steffi."

'SHE WILL NOT MISS'

Both players, who have never played each other on grass, have been in fine form at the tournament.

Defending champion Williams has dropped just one set on her way to the final, culminating in her 48-minute demolition of Elena Vesnina in the last four. Kerber has not dropped a set, and impressively outgunned Williams' sister Venus in the semis.

Williams leads left-handed Kerber 5-2 in matches since their first meeting nine years ago, and last season she won three of the four majors, including Wimbledon, only to stumble with a calendar-year Grand Slam in sight at the U.S. Open.

After Kerber denied her Graf's milestone at the Australian Open, Williams lost to Spain's Garbine Muguruza in the French Open final.

Her experience is almost unparalleled though: this is her 28th grand slam singles final, and ninth at Wimbledon, compared with her opponent's solitary major final appearance in Melbourne.

Whatever happens in Saturday's final, Williams will retain her number one ranking while Kerber will move onto her shoulder into second spot, from fourth.

If the match is anything like the 6-4 3-6 6-4 Australian Open encounter, the Center Crowd is in for a nail-biting classic with both players stretching each other to their limits.

Kerber knows what she must do to thwart the champion's march on history once again.

"I have to be aggressive, go for it, try to win the match and not hope she will miss. She will not miss." 

(Reporting by Pravin Char; editing by Martyn Herman)