Mertens' BJK Cup dash ominous for Aussies

Star turn Elise Mertens has come up trumps to salvage Belgium's hopes in the Billie Jean King Cup - and she could now threaten Australia's progression to the semi-finals in a winner-takes-all contest in Glasgow.

Mertens had to dash from the WTA Finals in Texas on Sunday where she had won the doubles title - almost missing her three-leg marathon journey in the process - before arriving in Scotland late on Tuesday night.

Clearly in no state to play in Wednesday morning's singles against Slovakia, Mertens, the world No.29, had to watch in disappointment as teammates Maryna Zanevska and Ysaline Bonaventure both lost their rubbers.

But with the tie already lost, Mertens emerged for the doubles, playing superbly in a handsome straight-sets victory for the loss of just three games alongside Kirsten Flipkens.

Despite the overall 2-1 loss to Slovakia, who had been beaten 2-1 by Australia on Tuesday, the doubles keeps Belgium's hopes alive as they meet Alicia Molik's team in the decider on Thursday.

Australia will qualify for Saturday's semis if they win the tie, but the Belgians will go through if they win 3-0.

If Belgium win 2-1, it will come down to the number of sets won and lost, so Australia could still potentially lose and go through.

Belgium captain Johan van Herck said he knew the doubles win was "our only chance to stay alive" as he heaped praise on Mertens' efforts.

"It was quite clear that Elise to play singles was not an option ... It's already amazing to see the level she gets being here, arriving yesterday evening at 10.30pm at the hotel, and see the attitude of what she brings on the court. Pretty amazing."

Mertens revealed that after winning the end-of-season WTA doubles with Veronika Kudermetova in Fort Worth, she had to rush to the airport, check-in with just two minutes left and sprint for the gate to catch the first of three flights via Madrid and London to Glasgow.

"I was, like, 'Oh my god, I'm not going to make it'. We rushed. I barely showered. You smelled it yesterday evening (when I arrived)," she laughed.

Asked if she will play in the key rubber against Australian No.1 Ajla Tomljanovic on Thursday, Mertens, the highest-ranked player in the tie, said: "We have to discuss it with everyone - who is ready to play, who is maybe less ready to play - but it's definitely an option."

Slovakia's Viktoria Kuzmova, who had lost to Tomljanovic on Tuesday, and Anna Karolina Schmiedlova - beaten by Australia's other singles player Storm Sanders - both rebounded with singles wins but it was not enough to keep their team in the tournament.

In the other early tie, Belinda Bencic beat Jasmine Paolini 7-5 6-3 and Jil Teichmann saved a match point en route to beating Elisabetta Cocciaretto 6-3 4-6 7-6 (7-5) as Switzerland defeated Italy.

World No.13 Paula Badosa won her Cup debut 6-2 3-6 6-4 against Kazakhstan's Elena Rybakina to give Spain a 2-0 lead in their Group C clash.

The Spanish could move into the semi-finals if they beat hosts Great Britain on Thursday.

In the late match, the United States' 'McCoco' pair - Coco Gauff and Caty McNally - won their decisive doubles match over Poland's Magda Linette and Alijca Rosolska 6-1 6-2 to clinch the tie 2-1.