Lapentti played four three-set matches last week, including his loss in the final to Chile's Fernando Gonzalez at the Vina del Mar claycourt event. He also went the distance in the first round here against Argentine qualifier Leonardo Olguin.
Argentina had three players reach the quarterfinals on Wednesday. Franco Squillari was leading, 6-1, 3-1, when sixth seed Alberto Martin of Spain retired due to injury. Chela will square off against compatriot Squillari in the quarterfinals.
No. 9 David Nalbandian also advanced, edging Fernando Gonzalez of Chile, 6-3, 1-6, 7-6 (7-5). Nalbandian will face another Chilean player in the quarterfinals as Nicolas Massu moved on after a 6-4, 6-3 win over Spain's David Sanchez.