After losing the first set, King got into some real trouble in the second set tie-break, staring down match point twice - Errani led 6-5 and 7-6 in the breaker - but King never stopped fighting, squeaking out that tie-break and edging the No.2-seeded Italian in a two-hour, 41-minute grinder, 26 76(7) 63.
It was a different kind of day for the No.1 seed, Li Na, who beat Nadiya Kichenok, 61 64. There was a little bit of a hitch - Li was originally leading 61 42 when Kichenok snuck out two games in a row to tie it up at 4-all in the second set - but the Chinese raced through a pair of love games to close it out.
"This is my first tournament since I changed to the new service motion, so it's still not very stable," Li said. "I hope with some more matches here it will become more stable going forward into the year."
Awaiting Li in the quarterfinals is Monica Niculescu, a 26 63 60 winner over Chan Yung-Jan. Niculescu actually beat Li in their only previous meeting, in front of the Chinese's own home crowd, no less.
"Monica plays quite differently than most of the girls," Li said of the Romanian. "My last opponent and today's opponent were more baseliners, but Monica sometimes plays slice and sometimes plays flat, so I need to keep focused on the court and play exactly according to my plan. I'm looking forward to it."
No.5 seed Peng Shuai, who won her second round on Tuesday, will also be in Thursday's quarters.