Sergiy topped American Robert Kendrick 6-3, 7-6(6) at the Regions Morgan Keegan Championships Tuesday to reach the second round in Memphis.
In addition to hitting 10 aces, Stako was almost unstoppable when he got his first serve in play, winning 25 of 27. He converted one of two break point chances and never faced a break point en route to a 72-minute victory.
The 26-year-old from Kiev will take on either Ernests Gulbis or Milos Raonic next.
Stako retired with a fever against Alex Bogomolov Jr. in the second set of his opening match Wednesday at the ABN Amro World Tennis Tournament in Rotterdam.
At 3-6 1-0, Sergiy walked over to his opponent and shook the Russian player’s hand, unable to continue.
Stako followed up his singles victory on Friday by teaming up with Denys Molchanov to dismiss Guillaume Couillard and Thomas Oger 6-2, 7-6(3), 6-4. The victory means that Ukraine moved into an unassailable 3-0 lead and reached the second round of Davis Cup Europe/Africa Zone Group II.
Ukraine next plays either Cyprus or Morocco in April hoping to return to Group I.