Comeback kid Ash Barty showed there was plenty of life in her second tennis coming on Wednesday night as she delivered a major scare to Australian Open champion Angelique Kerber at the Brisbane International.

And in Perth, Roger Federer is out of the Hopman Cup after an upset by Germany’s teenage sensation Alexander Zverev – skip down to read that report.

In Brisbane, the German world No.1 Kerber was forced to dig deep to survive a second-round fright at Pat Rafter Arena, eventually winning 6-3 2-6 6-3 in one hour 44 minutes, after being on the ropes.

Angelique Kerber shake hands following their second round competition at the Brisbane International. Photo: AAP/Dave Hunt

Barty defied her world ranking of 271 to rip through the second set in 33 minutes and have all the momentum in front of a raucous crowd.

A state Twenty20 cricketer just 12 months ago with the Brisbane Heat, she slugged it out with the dual grand slam champion and made her look second-rate in the one-sided second set.

But Kerber lifted in the decider, breaking the local favourite immediately and then keeping her foot on the throat to book a quarter-final encounter with sixth-seeded Ukrainian Elina Svitolina.

While disappointed at the result but pleased with her display, Barty promises to propel herself back into the top 100, and lower, in quick time with her freewheeling style of play.

She hit winners from all parts of the court and it was just her consistency which let herself down at times during the first and third sets, as well as Kerber’s superior movement.

The 2011 Wimbledon junior champion only returned to the sport last autumn after a two-year break as she fought loneliness and depression as a teenager on the tour.

Rediscovering her love of the game under new coach Craig Tyzzer has put the 20-year-old back on the path to being one of the country’s best players on the WTA.

Doubles partner Casey Dellacqua rated Barty the most talented Australian woman to emerge in the past decade and on her Brisbane form she showed she can also do damage as a wildcard at the Australian Open in less than a fortnight.

Barty rated the encounter the perfect start to the year for her, especially being forced to play aggressively to challenge Kerber.

Ash Barty leaves the court after her defeat. Photo: AAP/Dave Hunt

“I’m really really pleased with the form, a bit disappointed we didn’t win but very good things came out of it,” she said.

“It’s the start of good things to come hopefully.

“I’m a more developed player this time around.”

Kerber was full of praise for the 20-year-old and expected her to quickly rise up the rankings if she stayed injury free.

“Working hard and playing like she did tonight I’m sure she will have great results,” she said.

“She played so well straight from the first point tonight.”

– Jim Morton

Zverev upsets Federer at Hopman Cup

Roger Federer has hit a road bump on his comeback trail ahead of the Australian Open, losing to German teenage sensation Alexander Zverev in three sets at the Hopman Cup in Perth.

German teen sensation Alexander Zverev in action in Perth. Photo: AAP/Tony McDonough

The 17-time grand slam title winner went down 7-6 (7-1) 6-7 (4-7) 7-6 (7-4) in an enthralling two-and-half-hour encounter.

But in spite of the loss, Federer is happy with his lead up to the Australian Open, after six months on the sidelines with ankle and back injuries.

“Who really cares,” the 35-year-old said.

“As long as I am playing injury free and feeling good. I actually pulled up really good after the first match and the mixed, the next day, so this one will feel different.

“I’ll feel muscle pain, which is also one of the reasons why I came here, to have that pain in my body, so hopefully if I do have a tough match at the beginning in Melbourne I don’t have to go through it as extreme over there.

“I’m very happy. I have played five good sets so far. I am very pleased.”

Alexander Zverev has beaten former world No.1 Roger Federer for the second time in his career. Photo: AAP/ Tony McDonough

19-year-old Zverev, ranked 24 in the world said that he knew if he remained focused, a chance would come his way against the Swiss great.

“Against Roger you know you have to play every single point or you have no chance,” Zcerev said.

“You have to play it at a very high level otherwise he will beat you quite easily.

“It has always been like that and always will be until he stops playing.”

There wasn’t much between the two players, but Zverev, who is 16 years younger than Federer, just wouldn’t go away; and with his first serves consistently clocking over 200km/h he showed why he’s attracting so much world attention.

The win took his record over Federer to 2-1 having beaten the 35-year-old in Halle, in Germany before Wimbledon last year.

Pool B victor the USA has already booked its place in Saturday’s final and will face the winner of Friday’s tie between Switzerland and France, when Federer meets Richard Gasquet.

– Brad Elborough

Serena Williams slams Auckland conditions after loss

Meanwhile an upset Serena Williams has described her error-ridden defeat to American compatriot Madison Brengle in the ASB Classic in Auckland as “unprofessional’.

The top seed didn’t hold back in assessing her performance after the shock exit, and after a news conference it was clear she couldn’t wait to leave the city for Melbourne.

Serena Williams in a celebration of a point in her ASB Classic match. Photo: Anthony Au–Yeung/Getty

The world No.2 and winner of 22 grand slam singles titles lost her second-round match to fellow American Madison Brengle 6-4 6-7 (3-7) 6-4.

She struggled with the windy conditions in Auckland on Wednesday, producing a host of unforced errors – 88 according to one count – against a dogged opponent who kept returning the ball.

She said she “abhorred” the conditions, which were “just way too much for me”, but also acknowledged that Brengle had had to put up with them as well.

“I can take solace in the fact the conditions won’t be like this in Melbourne (for the Australian Open),” said Williams after just her second match in four months.