Medvedev broke for 4-3 in a tense opening set, then held for 6-4, with Gaston saving break points in holds for 2-1 and 4-5.
Medvedev broke for 2-1 and again for 5-2, clinical in taking 6-2, with Gaston's sole resistance a 7 minute hold for 2-3 saving both break points.
Medvedev broke for 1-0 after Gaston saved one of two break points, then held for 6-4 as Gaston mounted only routine resistance.