(Writes through with quotes, adds byline)
* Williams whacks herself in mouth with racket
* Says rolled ankle pain-free
* Serves 207 km per hour ace to seal match
By Ian Ransom
MELBOURNE, Jan 17 (Reuters) - Serena Williams added a fat lip and a bruised ego to her rolled ankle at the Australian Open on Thursday, after smacking herself in the mouth with her racquet during an otherwise fuss-free thrashing of Spain's Garbine Muguruza in the second round.
The 31-year-old American has endured a tough run at Melbourne Park in recent years, missing the tournament in 2011 due to injury and being bundled out of the fourth round last year after straining ligaments in her left ankle in the leadup.
Fears of another early exit were stoked when Williams rolled her right ankle against Edina Gallovits-Hall in her 6-0 6-0 demolition on Tuesday, while reports of an indoor training session the day after fuelled the intrigue.
Williams emerged, however, into the baking heat of Rod Laver Arena and duly pummelled the 112th-ranked Muguruza 6-2 6-0 in 75 minutes.
There was no discomfort with her ankle, said Williams, who despite being on pain-killers confirmed she would team up with her sister and long-time playing partner Venus in their doubles match later on Thursday.
"I didn't feel anything today," Williams told reporters. "Obviously when you go out to play you're heavy on adrenaline and you're really pumped up.
"Usually I feel injuries after the match, but so far, so good. I felt pretty, much better than I ever dreamed of expecting to feel."
The short-priced favourite to win her 16th grand slam and third in succession, Williams suffered a couple of mishaps in the first set, but recovered from each to march into a third-round match with Japan's Ayumi Morita.
When leading 3-2 in the first set, Williams stumbled awkwardly when scrambling to chase down a forehand, losing the rally to concede a break point and grimaced with pain.
In the same phase of play she was dabbing at her top lip with her manicured nails, having struck herself on the mouth on the follow-through of a forehand, drawing blood.
"Today I hit myself in the face, I don't know what's going to happen on Saturday," she said court-side. "I'm hoping I'm going to hit some winners.
"I figured if (the lip) gets swollen I'll at least have super sexy lips, right?"
Williams said she thought she had suffered a similar self-inflicted wound in the past, but had no recollection of serving faster than the 207 km per hour rocket she blasted to seal the match with her 10th ace.
She took to Twitter immediately to crow, posting: "What was that? That was 207km yes 128mph serve! Wha wha whatttt chu say??!!!! Whoop whoop!"
Williams joked it was the fastest she could remember landing in. "I did not expect to hit 207, I was shooting for 200." (Editing by Peter Rutherford and Amlan Chakraborty)