Marat Safin, just a few weeks short of retirement, knocked out top seed Nikolay Davydenko 4-6, 6-4, 6-2 in a high-profile first-round tie between the two Russians at the Kremlin Cup on Wednesday.
In-form Davydenko, who won last week's Shanghai Masters to climb to number six in the world, looked fatigued and jet-lagged following his long flight from China and bowed out to his friend and Davis Cup team mate after one hour 55 minutes.
Former world number one Safin, cheered on by a lively Moscow crowd, made sure his final appearance at his home tournament would last at least another day and played some inspired tennis to dismantle Davydenko in the deciding set.
"At this stage any match could be my last," said Safin.
"Actually I was a bit nervous facing Nikolay because he's been in such a great form lately but I served and returned well and capitalised on his mistakes."
Davydenko stayed in the running for a place in next month's World Tour finale in London despite the defeat.
Women's third seed Agnieszka Radwanska was not so lucky, a first-round 6-3, 6-3 defeat by former doubles partner Maria Kirilenko effectively ended her hopes of qualifying for next week's season-ending tournament in Doha.
"It was a tough match today, I was feeling a bit tired and exhausted," said the Pole, who was battling with Russia's Vera Zvonareva and Serbia's Jelena Jankovic for the last remaining spot in the $4.55 million extravaganza.
"I was trying because I was still in with a chance for Doha, but the surface is so slow here, you need to run a lot to win the point. Maybe if it was a faster surface, like grass, it would have been better for me but it wasn't my day today."
FIRST VICTORY
Kirilenko, who had lost in the first round in all her four previous appearances in Moscow, was delighted with her victory.
"To beat a seeded player in your first match is a great way to start a tournament. I've played her three times now and I won twice so I knew what to expect from her," said the Russian world number 61, who also beat Radwanska in the second round of the US Open last month.
"I actually like to play her because she is not very aggressive and I always have enough time to hit winners."
Italy's fourth seed Flavia Pennetta followed Radwanska out of the Russian capital when she retired with a knee injury midway through the second set of her first-round match against Hungary's Agnes Szavay.
Russia's sixth seed Elena Vesnina was upset, going down to 127th-ranked compatriot Evgeniya Rodina 6-1, 3-6, 6-2.
Last year's surprise men's champion Igor Kunitsyn was also knocked out, losing to fellow Russian Evgeny Korolev 7-6, 6-3.
Uruguay's fifth seed Pablo Cuevas became the first player to reach the quarter-finals when he prevailed over burly Russian Teimuraz Gabashvili 3-6, 6-1, 6-4.
Third seed Mikhail Youzhny of Russia joined Cuevas in the last eight after thrashing Italian Potito Starace 6-1, 6-1.
But France's seventh seed Fabrice Santoro was upset by Ukrainian qualifier Sergiy Stakhovsky 7-5, 6-1.
