Recent No. 1 Jelena Jankovic lost her third straight match when she was upset by Gisela Dulko of Argentina 6-4, 7-6 (5) at the Sony Ericsson Open early yesterday.

The final match of the second round ended at 12:20 a.m.

Jankovic, last year’s runner-up, blew a 5-2 lead in the second set and another 5-2 lead in the tiebreaker to Dulko.

The third-seeded Serb also lost her opening match at this month’s BNP Paribas Open.

Top-ranked Serena Williams reached the third round by beating teenage wild card Alexa Glatch 6-2, 6-3, leaving only two American women in the draw.

The other was Venus Williams, who beat Shahar Peer of Israel 6-3, 6-3 in her opener. Seeded players had first-round byes.

On the men’s side, top-ranked Rafael Nadal opened a bid for his first Key Biscayne title by beating Teimuraz Gabashvili of Russia 6-2, 6-2 and fourth-seeded Andy Murray was broken three times as he struggled to put away Juan Monaco of Argentina 4-6, 6-3, 6-2.

Murray, coming off a loss to Rafael Nadal in the BNP Paribas Open final, improved his career-best start to 21-2. His only other loss was at the Australian Open to Fernando Verdasco, who on Saturday took care of German qualifier Benjamin Becker 6-3, 6-4 to notch his 200th career ATP win.

Eighth-seeded Verdasco was in career-best form, having helped Spain win the Davis Cup final late last year, then reaching the Australian Open semifinals, and Indian Wells quarterfinals.

Other winners included David Ferrer of Spain, Fernando Gonzalez of Chile and Radek Stepanek of the Czech Republic, but No. 14 David Nalbandian was upset by Viktor Troicki of Serbia 6-1, 6-3.