Jack Sock of USA advanced to the third round of the Miami Open presented by Itaú after Sergiy retired in the second set.
The 22nd-seeded Sock was leading 6-3, 3-2 on Saturday when Stako retired. It was their first career meeting. The American broke twice in the first set and once in the second, having saved the only break point Sergiy earned.
Match statistics: aces (4-4), double faults (4-2), total points won (34-49).
Sergiy recorded his second ATP match win of the year by beating wild card Nicolas Jarry of Chile 7-6 (7), 7-5 in one hour and 30 minutes on Thursday at the Miami Open presented by Itaú.
After winning the first set tie-breaker, Stako went on to take the second set 7-5 breaking his rival in the 11th game and serving it out for a second round meeting with no.22 seed Jack Sock (USA). The Kiev native won 92% of points on his first serve.
Stats: aces (6-7), double faults (6-3), total points won (78-69).
No.2 seed Sergiy was forced to withdraw from Open BNP Paribas Banque De Bretagne Quimper semi-final clash with Andrey Rublev with low back injury which he sustained during the warm up.
The Kiev native reached the last four at the ATP challenger tournament with victories over Aslan Karatsev (7-6, 7-6), Alexandre Sidorenko (6-4, 7-6) and Romain Jouan (6-4, 6-7, 6-1).
In the doubles competition, Stako and Michal Mertinak fell in the quarter-finals.