Veteran Jurgen Melzer gave Pablo Carreno Busta a scare in the first round of the Kremlin Cup, but the Spaniard fought back to claim victory.
Carreno Busta, seeded sixth in Moscow, fell a set behind to his 35-year-old opponent before digging himself out of a hole to triumph3-6 6-3 7-6 (7-2).
Tuesday's schedule was marked by several retirements, with three of the seven matches halted by the withdrawals of Marcel Granollers, Mikhail Kukushkin and Aslan Karatsev.
All three retirees were losing at the time, with Stephane Robert, Daniil Medvedev and Evgeny Donskoy the beneficiaries.
Seventh seed Pablo Lorenzo beat Federico Gaio 6-4 6-4, and there were wins for Fabio Fognini and Dusan Lajovic.