Jankovic was not at her best but found a way to win in California
Jelena Jankovic won a marathon match to reach the fourth round of the BNP Paribas Open at Indian Wells in California but Kim Clijsters went out.
Serbian sixth seed Jankovic beat Italian Sara Errani 2-6 7-6 (8-6) 6-4 in two hours, 48 minutes.
Former world number one and two-time champion Clijsters tumbled out 6-4 1-6 7-6 (7-4) to Russia's Alisa Kleybanova.
Third seed Victoria Azarenka also made a premature exit, losing 7-6 (7-4) 6-2 to Maria Jose Martinez Sanchez.
Jankovic racked up 57 unforced errors, compared to Errani's 42, to clinch victory when the Italian made a hash of an overhead smash after a protracted rally.
"It was really a battle out there, and I just tried to stay positive as much as I could," said Jankovic, a semi-finalist in 2008. "I just tried to fight for every point and kept going and kept going.
"I couldn't really play consistently the whole time. I would play a couple of points well and then I would just give away a lot of points. I would give, in a way, a lot of gifts."
Errani had been bidding to beat a top-10 player for the first time in 12 attempts and she broke the world number nine three times to sweep through the opening set in only 31 minutes.
Jankovic squandered a 3-1 lead in the second, along with five set points in the tiebreak, but levelled the match with a crunching forehand winner down the line.
The final set was also an up and down affair, with Errani being broken three times and Jankovic twice but the Serb made her greater experience count.
After trailing 2-4, she won the next four games to reach the fourth round for the third time in four years.
Jankovic will now meet 17th-seeded Israeli Shahar Peer, who beat ninth seed Flavia Pennetta of Italy 6-4 6-7 (4-7) 6-1.
Clijsters, who returned to competition in 2009 following a two-year retirement and won her second US Open title in only her third tournament back, appeared to regain control after losing a tight opening set to Kleybanova.
The 26-year-old Belgian broke her opponent four times to storm through the second set and raced into a 4-0 lead in the third-set tiebreak before losing momentum.
After the 23rd-seeded Russian had clawed her way back to 4-4, Clijsters netted a backhand, struck a forehand wide and then dumped a forehand into the net to lose the match.
Earlier, holder Vera Zvonareva of Russia comfortably advanced by beating Latvia's Anastasija Sevastova 6-2 6-3.
And eighth-seeded Australian Samantha Stosur crushed Anastasia Pavlyuchenkova of Russia 6-3 6-0.