He is scheduled to play in Barcelona next week, then Estoril and the Rome Masters.
Anastasija Sevastova of Latvia beat Spain's Arantxa Parra Santonja 6-2 7-5 to win the women's final in Estoril.
Meanwhile at the ATP event in Estoril, second seed Richard Gasquet of France reached the third round in fine style.
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Fourth seed Tim Henman defeated Spanish qualifier Oscar Burrieza 6-3 6-4 to advance through to the second round of the Estoril Open on Tuesday.
Del Potro had beaten Montanes for the Estoril title in April.
The Australian set the fastest time of one minute 37.188 seconds at Estoril on Saturday to head off Honda teammate Dani Pedrosa and British rider Cal Crutchlow.
However, my favourite has to be Toni Elias passing both Rossi and Kenny Roberts Jr sideways into turn one of the final lap at Estoril in 2006.
The 22-year-old, who finished tied for 15th on Sunday in Estoril, now has a free week, having failed to qualify for Thursday's US Open at Pebble Beach.
She won her first two tour titles at Estoril in May and Linz last month, earning her a spot in this week's season-ending champions event in Bali.
Valentino Rossi suffered no such trouble as he guided his own Yamaha to the fastest time of the day, clearly putting those Estoril set-up problems firmly behind him.
Rossi, who failed to make the podium for the first time at Estoril in the premier class, seemed out of sorts on his Yamaha - eventually finishing 23 seconds adrift of Lorenzo.
As a neutral country during World War II, Portugal played host to spies, deposed royalty, black marketers and many others who came to stay at the hotel and play in the casino on the Estoril Coast outside Lisbon.
Federer's route to a second success in Estoril has been made easier by the withdrawal of Croatian second seed Ivan Ljubicic, who has pulled out due to the stomach strain that ended the world No. 14's campaign in Rome.
Federer is on track to win back the title he claimed on his only other appearance at Estoril in 2008, but admitted he was not yet at his best ahead of Saturday's semifinal clash with defending champion Albert Montanes.
Davydenko is enjoying his best year on the ATP Tour with two titles in Adelaide and Estoril and could join Andre Agassi and Roger Federer as the only players to have won at least three events this season if he wins the final.
But, after a tie for 46th at Celtic Manor and last week's efforts at the Estoril Open de Portugal, where he shot two 69s and a third round 66 before falling away with a final day 76, he has taken the advice of his manager Chubby Chandler to free wheel for a few days.
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