Jelena Jankovic responded to a first-set thrashing to beat Elise Mertens and book her place in the quarter-finals of the Mallorca Open on Wednesday.
The second seed was blown away in a one-sided opening set, but recovered to see off the Belgian qualifier 0-6 6-4 6-3.
Jankovic also failed to hold serve in the first game of the second set, but the Serb broke straight back and got into her rhythm to level the match and set up a decider.
Mertens broke Jankovic yet again in the first game of the final set, but the favourite dug deep to win five games in a row from 2-0 down and set up a last-eight clash with Sorana Cirstea, who beat Daniela Hantuchova 6-3 6-4.
"It was a very, very tough match," Jankovic said. "I played against a young opponent who came through qualities and has done quite well recently.
"She's played a lot of matches on grass and so she's quite confident."
Eugenie Bouchard, the number eight seed, was surprisingly consigned to a 6-3 6-3 defeat by Latvian Anastasija Sevastova.
Sevastova's victory set up a match against Mariana Duque-Marino, who beat Sabine Lisicki in three sets after dropping the opener 6-1.