PRAGUE, Czech Republic - No.1 seed Simona Halep was made to work for the second round in a row at the Prague Open, needing to come from a set and a break down in both the second and third sets against Barbora Krejcikova before quelling the wildcard and moving into the quarterfinals 3-6, 7-5, 6-2 in two hours and five minutes.

"I didn't feel great," she said after the match. "My energy was not great, but sometimes it's more important to win matches you're not playing so great in, and you just find a way to fight and win it."

Having needed a deciding tiebreak and seven match points to fend off Polona Hercog 6-1, 1-6, 7-6(3) in the first round, the Romanian - who took a medical timeout for her shoulder after the second set and was beset by 10 double faults - once again found herself stretched to the limit by an idiosyncratic opponent, against whom she faced a point to go down a double break in the third set.

"It's never easy to play someone who is so good in doubles, because she hits different angles, which makes it very interesting and very difficult. It wasn't a very good level from me, in my opinion, but the most important thing is that I was able to win."

In coming from a set behind today, Halep reprised her comeback in the only previous meeting between the pair, in the first round of Bucharest 2016, which she took 3-6, 6-1, 6-1 en route to the title.

"Today I didn't feel so great with my energy. It took me time to get ready for the match, but she was playing so well, so it wasn't just about me on court. I just tried to stay calm."

Since then, both players have gone on to the World No.1 ranking and multiple Grand Slam trophies, Halep in singles and Krejcikova in doubles. Despite the latter's relative low ranking and paucity of accomplishments in singles, in which discipline she is yet to post a Top 30 win, the four-time doubles major champion's elite talent, honed with late mentor Jana Novotna, is no secret - and it was very much on show during stretches of today's match before Halep asserted her authority, reeling off the final six games in a row for a 'hidden bagel' that belied how tough the contest had been.

Both players were tentative out of the blocks, with the first four games of the match seeing four breaks of serve - two of them, once from each player, conceded with a double fault down break point. Halep, though, appeared to have the tactical measure of her opponent: relentlessly directing traffic to the Krejcikova backhand invariably elicited an error eventually in the early stages.

But it was the lower-ranked player who gathered herself first - and once she did, she accelerated ahead rapidly. Three consecutive service winners from Krejcikova paved the way to the first hold of the match, starting a run of 12 out of 14 points for the home player as she raced into a 5-2 lead. Efficient at net and with her big forehand, this lead was sufficient for Krejcikova to close out the set against an uncharacteristically low-intensity Halep.

This would change as the second set got under way. Though Halep slipped down an immediate break, this deficit seemed to spur the Wimbledon champion into action. Hustling around the court with greater alacrity than before, Halep began to come up with some of her best trademark defensive plays: a pinpoint lob in the second game en route to breaking back, chasing down several Krejcikova droppers to flick passes past the Czech, delivering stunning down-the-line drives on the run to turn defence into offence. Moreover, the World No.2 was taking Krejcikova's best shots on with relish, evidenced by running around a formidable body serve to pummel a clean forehand return winner to break again for 3-1.

But for all of Halep's improvement, double faults continued to plague the Romanian, hampering her efforts to maintain her lead. A fifth down break point enabled Krejcikova to break back for 3-2; three followed in the seventh game, and though Halep overcame those to hold for 5-2, a ninth was responsible for squandering the third of four set points as she served for the set at 5-4.

This made closing out the set rather more complicated, particularly when the 2017 Nurnberg runner-up, sensing opportunity, began to surge with her shotmaking again, finding a number of neat backhand winners down the line in the latter stages of the set. But, having been pegged back to 5-5, Halep hung tough, continuing to look for aggressive openings with her forehand. Two winners from that wing brought up more set points on the Krejcikova serve at 6-5, and Halep eventually converted her sixth as a Krejcikova backhand sailed long.

If the wildcard feared that the match would follow the same pattern as their Bucharest battle four years earlier, it didn't show as the deciding set got under way. Swatting forehands away with relish, Krejcikova powered to an immediate break - and had a point for a 3-0 double break, too. But her slice backhand - a weakness throughout the day - let her down after an epic all-court rally, and with that chance gone Halep was once again able to clamber back into the match.

The former World No.1 still needed to survive a break point and two deuces at 2-2, but having passed that test finally began to take a semblance of real control. Crucially, Halep's serve was beginning to behave, with just one double fault in the deciding set balanced against a greater number of clutch service winners to hold Krejcikova at bay. The lower-ranked player was also beginning to crumble, with her backhand again repeatedly letting her down on both the drive and the slice; by the time she served to stay in the match down 2-5, Krejcikova was hitting out all too wildly, with a third double fault sealing a love break to conclude the contest.

Next up for Halep is lucky loser Magdalena Frech, who reached her maiden WTA quarterfinal earlier with a three-set win of her own, the Pole overcoming Arantxa Rus 6-3, 2-6, 6-4 in two hours and eight minutes.

2020 Prague highlights: Halep comeback halts Krejcikova