PERTH, Australia -- The first three-set battle of the inaugural United Cup saw Despina Papamichail come from a set and a break down to defeat Isabella Shinikova 3-6, 6-4, 6-1 in 2 hours and 19 minutes. It was swiftly followed by the second, which saw Stefanos Tsitsipas edge Grigor Dimitrov 4-6, 6-2, 7-6(4) to give No.1 seeds Greece a 2-0 lead over Bulgaria.

It was the second time in the past three months that Papamichail had defeated Shinikova from a set down, having previously won 3-6, 6-3, 7-6(3) in a Monastir ITF W60 tournament in October.

Initially, Shinikova's heavier weight of shot prevailed. The 31-year-old built an early 3-1 lead, and resisted a comeback attempt from Papamichail to survive eight deuces and regain the break for 4-2.

Sakkari, Tsitsipas drawing on fond memories in Perth for United Cup

But trailing 2-1 in the second set, Papamichail's tenacious qualities shone through. The Greek player began to find a plethora of winners, with her backhand particularly impressive, and delivered a near-flawless passage of play to level the match.

An ailing Shinikova required strapping on her left leg ahead of the third set, and on resumption her struggles on serve were evident. The No.381-ranked Bulgarian managed to take an early break again, but was unable to sustain the rally tolerance required to hit through Papamichail. Cramps in her racquet hand midway through the set only added to Shinikova's woes, and Papamichail cruised through the last six games in a row.

"I'm playing with a really strong team," said Papamichail on court afterwards. "Maria [Sakkari] is a big example for me, so the least I could do was fight my heart out."

It was Papamichail who set the example on Day 1 of the United Cup, as Tsitsipas found something extra to clinch victory over Dimitrov in an opening-day thriller.

Dimitrov went toe-to-toe throughout the 2-hour, 10-minute encounter with Tsitsipas, producing some sharp returning en route to the first set against the ATP No.4. After Tsitsipas found his range to surge to the second, his big serve ultimately proved decisive in the closing stages as he capped a nailbiting win in the deciding-set tiebreak.

It was 24-year-old Tsitsipas' 250th tour-level win. The Greek was particularly cool under pressure in the final set, when Dimitrov’s controlled aggression carved out three break points, including two when trailing 3-4. Tsitsipas saved them all before charging to what proved to be an unassailable 5-2 lead in the tie-break as he extended his head-to-head record against Dimitrov to 6-1.

The ATP Tour contributed to this report.