Johanna Konta was unable to build on her round two efforts in Rome as she lost a tough three-setter to Japan's Misaki Doi on Thursday.
The Italian open draw appeared to have opened up for the British No 1 following her victory over seventh seed Roberta Vinci in round two but Doi proved the stronger in a 4-6 7-5 6-2 victory.
Konta stormed out of the blocks to take the opening three games and held off her battling opponent to take the first set.
She then fought back from two breaks down to draw level in the second at 5-5 but then suffered a major wobble, losing eight of the last 10 games.
Doi, ranked 45 to Konta's 23, was in the ascendancy and eased to victory in two hours and 21 minutes.
Top seed Serena Williams also booked her place in the quarter-finals with a 7-6 (9-7) 6-1 win over fellow American Christina McHale.
Williams will go up against ninth seed Svetlana Kuznetsova - who overcame fellow Russian Daria Gavrilova 6-2 2-6 6-3 - in the last eight. Doi will play Swiss Timea Bacsinszky.