Juan Ignacio Chela of Argentina overcame a big deficit in the tiebreaker and upset top-seeded Nikolay Davydenko 6-1, 7-6 (5) in the second round of the Pilot Pen in New Haven on Wednesday. Chela was cruising at 6-1, 3-0 before Davydenko rallied. The Russian won the next four games, but Chela held service to tie the set at 4-4. In the tiebreaker, Davydenko, ranked sixth, surged to a 4-1 lead but lost the next five points, two when he hit backhands into the net. Chela, ranked 50th, then hit a forehand into the net. But Davydenko ended a long rally and the match when his crosscourt forehand from the right corner sailed wide. Davydenko's baseline style helps Chela, who is unbeaten in four matches against him. The Russian increased the tension on his rackets for this tournament but, after falling far behind, switched back to one with less tension that gave him more control. Then, he started his comeback but broke his racket late in the match and went back to one with greater tension, AP reports.