Great Britain’s Heather Watson has got a secret weapon heading into the Australian Open, but she’s not going to let the cat out of the bag just yet.

Watson launched a fierce second-set comeback to beat Germany’s Andrea Petkovic in Friday’s Hopman Cup clash at Perth Arena.

The world No.75 Brit won the first set in 31 minutes, but the match appeared destined for a deciding set after Petkovic raced to a 5-1 lead in the second.

But Watson reeled off the next five games to send it to a tiebreak, before sealing the win 6-2 7-6 (7-3) in 92 minutes.

It gave Great Britain a 1-0 lead in the tie ahead of German star Alexander Zverev’s clash with Dan Evans in the men’s singles rubber.

Watson reached a career-high 38th in the world in 2015, but she has since slipped to 75th and into relative obscurity.

The 24-year-old has set her sights on breaking back into the world’s top 50 this year.

And she hopes to unveil something special in Melbourne.

“I’ve definitely started trying new things myself,” Watson said.

“It’s a secret. If it starts working for me, it’s going to stay a secret. If not, then I’ll let you know later.”

Petkovic is currently ranked 55th in the world, but the 29-year-old German wants to break back into the world’s top 20.

She reached a career-high ranking of ninth in 2011.

“It really sucks being out of the top 50, because you think you can do better, and you know you can do better,” Petkovic said.

“There were a few times where I played bad, a few times where the other girls played well. Hopefully I can turn it around this year.”

Petkovic finishes the Hopman Cup with just one singles win to her name – a straight-sets triumph over France’s Kristina Mladenovic.

She pushed former world No.7 Belinda Bencic to three sets on Wednesday night, but she was disappointed with her display against Watson.

“I wasn’t playing well today. My backhand was off,” Petkovic said.