Laura Robson brushed aside an injury-hit Venus Williams 6-3 6-2 to set up a second round meeting with the American's sister Serena at the Internazionali d'Italia in Rome today.
The British number one made light of difficult, blustery conditions to see off the former world number one, who was plainly struggling with the back injury that has blighted her season so far.
But it was a fine performance from the 19-year-old Robson, who showed no ill effects from her final set collapse against Ana Ivanovic last week which cost her a place in the Madrid quarter-finals.
Robson made a rocky start, serving two double-faults in her opening service game and saving two break points, but hit back to break Williams in the next game to take a 2-1 lead.
Robson's improvement on clay continued with the defeat of Williams
Williams, playing only her second clay-court event of the season following her return from injury, then double-faulted to hand Robson a double break.
The American had plenty of chances in the first set and spurned 10 break point opportunities before taking her 11th when Robson served for the set, only for Robson to immediately respond with her third break to take the opener.
Robson, whose contrasting week in Madrid last week also included a career-best win over world number four Agnieszka Radwanska, was in dominant form and continued her good form into the second.
With Williams beginning to struggle, Robson looked set to blaze home, breaking twice to go 5-1 up, but had to wait for her victory as Williams briefly rallied to claw one break back.
But there was no repeat of the nerves that had afflicted her against Ivanovic as Robson took advantage of her third match point chance on the Williams serve with a big backhand to wrap up an excellent win.
Robson will now face world number one Serena, who was watching from the stands, in round two.