Jetlagged? Getting thrashed? World No.1 Serena Williams came up with a winning answer for those conundrums – a coffee break.

Williams was staring down the barrel of an embarrassing loss after coughing up the opening set 6-0 inside 19 minutes to Italian Flavia Pennetta during their Hopman Cup clash on Monday.

Struggling for energy and flailing badly, Williams got a ball girl to fetch her an espresso during the break, and the caffeine hit did wonders as the 33-year-old won 10 straight games to secure the match 0-6 6-3 6-0 in 89 minutes.

“It’s miracle coffee,” Williams joked after the match.

“I am a coffee drinker. I didn’t have mine this morning and I was just feeling it, so I just had to get some coffee into me.

“I just asked them to get me a shot of espresso. I asked them if it was legal, because I’ve never done it before.

“I needed to wake up – it’s just the jetlag. It gets you all the time.”

United States took an unassailable 2-0 lead in the tie after world No.18 John Isner beat Fabio Fognini 5-7 7-5 7-6 (7-4) in a 147-minute epic.

Williams said the round-robin nature of the Hopman Cup meant she didn’t need to stress as much and her goal this year is to enjoy herself more on court.

“I’ve never smiled so much in a match before,” Williams said.

“This year my whole goal is to have fun.

“My dad says, ‘Serena, you’ve done everything, enjoy yourself, I promise you’ll play better’.

“So I’m like, ‘OK’. I’m trying to relax a bit more and play how I know I can play.”

The mercury in Perth nudged 44 degrees on Monday, but with the Perth Arena roof closed, the cool conditions should have ensured for a high-octane match.

Instead, Williams’s lethargy paved the way for a first-set romp, before the 18-time grand slam singles champion finally found her energy and fighting spirit.

Williams will face another stern test on Tuesday night when she takes on world No.6 Eugenie Bouchard of Canada.