Second seed Clijsters mixed six aces with 13 double faults against Errani but broke her opponent twice early in the third set to win a wildly fluctuating encounter in just under two hours at the Indian Wells Tennis Garden.
Champion here in 2003 and 2005, the Belgian failed to hold serve twice in the opening set and three times in the second as the gutsy Italian kept the former world number one under constant pressure.
"It wasn't my best tennis today," Clijsters said courtside after booking a place in the next round against 15th-seeded Frenchwoman Marion Bartoli, a 6-4 6-2 winner against Germany's Andrea Petkovic.
"I just felt a little slower on the feet. And serving, my shoulder has been bothering me for a while. On this surface against a player who plays with a lot of topspin, I just feel it a little bit more."
"I played a tricky player who played a good match, but I was still able to win without being close to coming to my best level. That's the positive thing."
Clijsters, who won the Australian Open in January, had not competed before this week for almost a month since losing to Czech Petra Kvitova in the Paris Open final.
She swiftly demolished Russian Alla Kudryavtseva 6-2 6-0 in her opening match on Friday but faced much tougher resistance from baseline battler Errani.
"I also know that for my next match everything will have to be a lot better," Clijsters said. "That's what my goal will be... trying to achieve that."
(flandersnews and reuters)
Wickmayer advances too
Belgium's Yanina Wickmayer (WTA 25) will meet Dominika Cibulkova of Slovakia in the next round of the WTA-tournament in Indian Wells.
Wickmayer beat Kaia Kanepi of Estonia (ranked 16th in the world) 3-6, 6-4 and 6-1 on Sunday. 21-year-old Dominika Cibulkova trounced Vera Zvonareva of Russia, the current world's number 3, in three sets: 6-4, 6-7 (4/7) and 4-6.
Cibulkova has only won one of her three matches against Wickmayer.
The winner of the tournament takes home 4.5 million dollars.