The 31-year-old Russian, without a win over a Top 10 player in 15 attempts, and without an appearance in a final for 21 months, clinched a stunning 6-2, 6-3 win over one of the tour's most tenacious players.
Davydenko beat the Spaniard with a bullying brilliance which reminded people a little of the successive victories he produced over Roger Federer and Rafael Nadal when he capture the title in Doha three years ago.
Cilic, Wawrinka ousted
Meanwhile, third seed Marin Cilic and No 4 Stanislas Wawrinka also crashed out of the Chennai Open yesterday even as second seed Janko Tipsarevic eased into the semi-finals.
Cilic, a two-time Chennai champion, was stunned by the 47th-ranked Benoit Paire of France, who won 6-4, 1-6, 7-5 on the showcourt of the Nungambakkam tennis stadium.
Wawrinka was waylaid by 23-year-old Aljaz Bedene of Slovenia, who advanced to his first-ever ATP semi-final with a 6-2, 7-6 (8/6) win in an hour and 31 minutes. The 86th-ranked Bedene’s opponent in the semi-final will be World No 9 Tipsarevic, who swept aside eighth seed Go Soeda of Japan 6-2, 6-4.