Sanguinetti is ranked 68 in the world, 65 places below Nalbandian

The Argentine was thrashed 6-1 6-2 by a player ranked 65 places below him.

Cypriot Marcos Baghdatis also made an early exit in his first outing since Wimbledon, the 10th seed beaten 5-7 6-2 6-3 by France's Julien Benneteau.

Fourth seed Ivan Ljubicic, fifth-seeded James Blake, Tomas Berdych (13th) and Fernando Gonzalez (15th) all advanced.

Ljubicic beat Spaniard Nicolas Almagro 7-5 6-1 while Blake coasted to a 6-4 6-1 victory over 17-year-old Canadian wildcard Philip Bester.

Berdych advanced with a 6-4 7-5 win over another Canadian wildcard, Daniel Nestor, while Chilean Gonzalez beat Sweden's Robin Soderling 6-3 4-6 6-2.

Sanguinetti, 33, beaten by Nalbandian at last year's US Open, took just 59 minutes to demolish the Argentine, who complained of feeling ill.

"I had a headache, a little bit of fever," said Nalbandian. "I didn't feel good enough to try to push myself to play well.

"I said to myself 'I want to try, I have nothing to lose. I'm not going to feel worse than this'. I tried, but nothing changed."

The opening day of the tournament also featured the joint longest tie-break in ATP Tour history.

Argentine Jose Acasuso beat Germany's Bjorn Phau 7-5 7-6, winning the tie-break 20-18 - the fifth time a singles tie-break has gone the distance first reached by Bjorn Borg and Premjit Nall at Wimbledon in 1973.

First and second seeds Roger Federer and Rafael Nadal return to action on Tuesday for the first time since their Wimbledon final.

Federer won in Toronto two years ago while in his absence last year, Nadal claimed his first hardcourt title.