Hewitt fell behind 5-0 in the second set, made a run back with breaks in the sixth and eighth games but stalled as he was broken in the ninth game of the set. Chela next faces compatriot Horacio Zeballos in the semi-finals.

Zeballos upset top-seeded Fernando Gonzalez of Chile 6-4, 6-4. American Sam Querrey also advanced, beating Chile’s Nicolas Massu 6-3, 3-6, 6-4. Querrey will face American Wayne Odesnik — who is playing even as he is being investigated by the International Tennis Federation and possibly facing a two-year ban —, a 6-4, 6-1 winner over Belgium’s Xavier Malisse.