"Every time I was going into a rain break I was going into different emotions," said Kostyuk, who was also emotional several times during the match.
Sakkari initially looked undisturbed by the rain suspension, taking the first set soon after the restart.
Her new training partnership with former Wimbledon finalist Mark Philippoussis looked to be paying off with Sakkari in complete control.
Kostyuk, however, turned the tables in the second set with aggressive play that forced Sakkari into more unforced errors.
Sakkari was wilting by then and Kostyuk took nine consecutive games en route to a 5-1 lead before sealing victory on her first match point.
Persons:
Ukraine's Marta Kostyuk, Greece's Maria Sakkari, Andrew Couldridge, Marta Kostyuk, Maria Sakkari, Kostyuk, Sakkari, Mark Philippoussis, Karolos Grohmann, Ed Osmond
Organizations:
Lawn Tennis, Croquet Club, Greece's Maria Sakkari REUTERS, Wimbledon, Ukrainian, Thomson
Locations:
London, Britain, Ukrainian