Sweeting downed Korolev 6-3, 4-6, 6-2 in opening round action at River Oaks Country Club.
Oft-injured American Taylor Dent withdrew with a hip injury during his match with sixth-seeded Argentine Horacio Zeballos after losing the first set 6-3, and No. 7 seed Eduardo Schwank of Argentina advanced with a 6-3, 6-2 pounding of Brazil's Marcos Daniel.
Also going down with injuries were Americans Mardy Fish and Michael Russell. Fish was replaced by Somdev Devvarman of India who promptly defeated Conor Niland of Ireland 6-4, 6-2.
American Michael Yani replaced Russell, and he was defeated by Mikhail Kukushkin of Kazakhstan 6-1, 7-5.