Former world number one Venus Williams scraped into the semi-finals of the Italian Open in Rome when she edged out Jelena Jankovic 5-7, 6-4, 6-1 on Friday.
Her rival for a place in Sunday's final is another former top-ranked player, Martina Hingis, who swept past home favourite Flavia Pennetta 6-3, 6-1.
Seventh seed Svetlana Kuznetsova survived a scare in ousting Italian qualifier Romina Oprandi 6-4, 5-7, 7-6 while Dinara Safina crushed fifth seed Elena Dementieva 6-1, 6-1.
Williams's usually strong serve let her down badly throughout her match with Jankovic.
The American, seeded nine, dropped serve four times on the way to losing the first set and showed no sign of steadying herself as she dropped her opening two service games of the second set.
It was only her ability to break straight back that kept her in the contest.
In the end it was Williams's superior fitness that made the difference. As the hot, humid conditions on Rome's centre court sapped the energy from Serbian Jankovic's legs, Williams took control.
She held serve in the ninth game of the second set to go 5-4 up then rallied to break and level the match before a clearly tiring and blistered Jankovic succumbed to the weight of Williams's groundstrokes in the decider.
"She played really well and it was difficult to play last night and then come out here again this afternoon. In the first set I made far too many mistakes," said Williams.
TOUGH MATCHES
Williams lost the 1998 Rome final to Hingis but got her revenge the following year when she beat the Swiss in the last four on the way to claiming the title.
"They have always been tough matches and great experiences. I'm sure this one will be just as tough," Hingis said after beating Pennetta.
Kuznetsova battled for almost two-and-a-half hours before overcoming Oprandi.
On paper, the contest between 2004 US Open winner Kuznetsova and Oprandi -- ranked 133 in the world and playing in the main draw of a WTA tournament for only the second time in her career -- looked like a mismatch.
After two tight sets, however, the Russian found herself a break down in the decider and had to save match point as she served to stay in the contest.
She eventually scraped through, firing a forehand winner past Oprandi and then unleashing a winning service return to snatch victory in the tiebreak.
Safina enjoyed a much easier passage past fellow Russian Dementieva, who sprayed a succession of shots long and wide and whose exit left Kuznetsova as the highest-ranked player in the event.
"I think the tournament is really open now," said Safina. "It's just a matter of who fights more and has more eagerness to win."