Viktor Troicki came from behind to beat Bernard Tomic in the first round of the TEB BNP Paribas Istanbul Open.
Troicki started slowly but found his groove with 13 aces and five breaks against the Australian, who was competing at this level for the first time this year.
The Serbian finished a 3-6 6-0 7-5 winner.
Paolo Lorenzi is also through to the next round after reaching the 100-win landmark with victory over Cem Ilkel.
The 36-year-old Italian has been on the tour for 15 years and brought up his century of successes by beating the local favourite 6-2 6-3.
His hopes of moving to 101 lie with Argentina's Marco Trungelliti, who came from behind to beat Elias Ymer 4-6 6-3 6-2.
Troicki's compatriot Laslo Djere also progressed, with an unexpected 7-6 (7/5) 7-6 (8/6) win over Denis Istomin, and Japan's Taro Daniel bettered Matteo Berrettini 7-5 6-3.
German wildcards Yannick Hanfmann and Matthias Bachinger were both successful in their first-round outings at Munich's BMW Open.
Hanfmann beat former world number eight Marcos Baghdatis 6-2 6-4 with Bachinger seeing off Mikhail Kukushkin in three sets.
They were not joined by countryman Florian Mayer though, after he fell to qualifier Martin Klizan.
At the Millenium Estoril Open Portuguese wildcard Pedro Sousa held his nerve in a decisive tie-break to beat Gilles Simon 6-3 4-6 7-6 (7/4).
Australian Alex de Minaur defeated Gastao Elias 6-3 6-1 and Frances Tiafoe ousted fellow American Tennys Sandgren in a lengthy encounter.