World number one Serena Williams claimed a landmark 700th career victory after overcoming a second set wobble to defeat Sabine Lisicki in the Miami Open quarter-finals.

The world number one, a 19-time grand slam champion, edged a first set tie-break against her 27th seeded opponent, who then took advantage of Williams' inconsistency to take the match to a decider.

Williams had uncharacteristically made 17 unforced errors in the second set alone but bounced back against the German in the third, opening up a 3-0 lead before triumphing 7-6 (7/4) 1-6 6-3.

She is the eighth woman in the Open era to reach 700 match wins - although she is still well behind the record holder Martina Navratilova, who claimed 1,442 career victories.

The 33-year-old American was presented with a cake following the match but admitted she was oblivious to her record.

"I had no idea," Williams said on the WTA Tour website. "I saw them bringing out a cake and I thought, 'Whose birthday is it today?' But I really had no idea about it, so I'm really excited right now."

Williams was less enthusiastic about her performance against Lisicki, adding: "Today wasn't my best day.

“I wasn't serving the way I normally serve or hitting the way I normally hit, so all I could do was just fight and try to give 200 per cent instead of 100 per cent."

Don't know how long she has left in her career, but when healthy she's one of the most dominant forces Women's tennis has ever seen. She could still have 2-3 slams left in her.