The No.9-seeded Bartoli came out stronger, winning eight points in a row from 1-all to build a 3-1 lead; but the No.6-seeded Errani flipped the script from there, winning seven games in a row for a 63 20 lead, and six games later she was a 63 62 winner and the tournament's first quarterfinalist.
"It wasn't easy - it was very hot out there and I didn't start well," Errani said. "But from 3-1 down in the first set I started to serve better, hit my forehand much better, moved her around more and was more aggressive when I needed to be, which is what I had to do. So I'm very happy about this match."
After losing their first meeting at the US Open in 2007, Errani seems to have Bartoli's number - she has beaten her three straight times now, having also beaten her at New Haven and Tokyo last year.
"This felt like a difficult court for me before - it was not easy the first few days," Errani said. "But match by match I'm feeling better. No matter who I play against next, I think I'll be ready to play."
"I watched Arruabarrena's match against Vinci and she's a very good player - I think she has amazing hands," Errani said. "And Sharapova is so strong - she's obviously a very good player and so tough.
"Whoever it is will be very tough, but I will try my best for sure."
And it was Sharapova who won that one, pounding 30 winners to Arruabarrena's six to prevail, 75 60. Arruabarrena was actually just a few points away from taking the first set - Sharapova was serving at 4-5 and fell behind 15-30 on her serve - but she won nine games in a row from there. She finished it off with some stellar serving - she hit four aces in her last seven service points of the match.
"The first set was so up and down," Sharapova said. "I knew I had to buckle down and start being more aggressive, stepping in on the returns and getting more first serves in. She was a tough opponent today but once I started playing more aggressively in the second set things went much better for me."
And on the hot conditions? "I've spent so many years of my life in Florida, and this dry heat is much easier than practicing there for a few hours," Sharapova commented. "It's actually a treat."
Sharapova has beaten Errani both times they've played, in the French Open final and the round robin of the WTA Championships last year. And she won both by the identical scorline, as well - 63 62.