Tsitsipas battles past Dimitrov at inaugural United Cup

Stefanos Tsitsipas fired his 12th ace on match point to give Greece a 2-0 lead over Bulgaria with a comeback win against Grigor Dimitrov on Thursday at the inaugural United Cup.

The world number four recovered smoothly after losing the opening set to emerge with a 4-6, 6-2, 7-6 (7/4) victory in his season-opening match at Perth ahead of the Australian Open.

Greek teammate Despina Papamichail, ranked 158th, gave her country the opening point as she defeated a cramping Isabella Shinikova, also finishing with a fightback to win 3-6, 6-4, 6-1.

The mixed teams tournament features 18 countries playing in Sydney, Brisbane and Perth, with each tie consisting of two men's and two women's singles rubbers along with a mixed doubles.

Tsitsipas lifted in the final-set tiebreaker against an opponent he has now defeated in six of their seven matches.

"It was extremely close, but I'll take it," he said. "It was a good effort from my side.

"It was tough playing in the heat -- I'm glad they closed the roof. I had to hang in there and fight, Grigor can compete with the best in the world.

"But I found a little gap and gave myself the chance to do something in the tiebreak."

In Sydney, American world number nine Taylor Fritz and 11th-ranked Madison Keys cruised through their opening ties against the Czech Republic to also get their seasons off to a winning start.

Fritz got his country away to a flyer with a 6-3, 6-4 victory over world number 74 Jiri Lehecka at Ken Rosewall Arena before Keys saw off Marie Bouzkova 6-4, 6-3.

The 25-year-old Fritz had a breakthrough year in 2022, beating 22-time Grand Slam champion Rafael Nadal in the final at Indian Wells to go with titles in Tokyo and Eastbourne.

He burst into the top 10 in 2022, reaching a career-high