Updated

By Julian Linden

MELBOURNE (Reuters) - If winning the Australian Open were a simple test of will power, Serena Williams would win every time.

While other players succumb to self-doubt and nerves when things start going against them, Williams never loses faith in her ability to dig herself out of trouble.

Williams booked her place in the final by beating China's Li Na 7-6 7-6 Thursday. She was expected to win so the result was no surprise but it was anything but a walkover.

Li, playing the match of her life, gave the world number one a torrid time, thumping into the ball deep into the corners and forcing the American to scamper from side to side.

Already heavily bandaged, Williams looked to be tiring fast but showed why she remains the most feared player in the game by raising her game when it mattered and dominating the tiebreaks.

"I am happy I was able to pull it out, it was really close," Williams said. "I wasn't at my best today but I'm still here -- which is shocking -- and I'm just going to do whatever I can to stay."

Williams may have looked close to exhaustion but she remains a glutton for punishment and has an endless love of playing the game.

A few hours after beating Li, she was back on court, teaming up with her sister Venus to beat Lisa Raymond and Rennae Stubbs and qualify for Friday's doubles final.

"I don't think it's flattened me. I think it's helped me," she said. "I get a lot of extra practice...I just like being out there."

(Editing by Alastair Himmer)