Perth - British number one Andy Murray conceded he was being troubled by a lingering left shoulder problem after he opened his Hopman Cup account with a straight-sets win over Frenchman Benoit Paire at the Perth Arena on Monday.
The world number six had few problems with Paire, himself on the comeback trail after injury, and won their clash 6-2, 7-5 as Great Britain beat defending champions France 2-1 at the mixed teams tournament.
Although the French levelled the tie when Alize Cornet thrashed Heather Watson, 6-2, 6-2, the Brits claimed the deciding mixed doubles in a match tiebreak, 6-4, 2-6, 10-8.
Murray suffered from soreness in the shoulder during and after his emphatic victory over Rafael Nadal in the season-opening tournament in Dubai last week, which he won when Novak Djokovic forfeited the final.
The dual Grand Slam champion subsequently had a scan which cleared him of any serious problems, however the shoulder again caused him discomfort in the win over Paire.
Just two weeks out from the year's first Grand Slam, the Australian Open in Melbourne, where he has been a finalist three times, the 27-year-old conceded the pain was causing him concern.
"It is still quite sore," he said.
"If it was my right shoulder it would probably be quite hard for me to play, I do not feel it on my groundstrokes as much but I feel it when I am serving.
"Maybe it was playing a match (in Abu Dhabi) after having a break or I just got it in the wrong position and tweaked something a little bit, but I should be fine."
Murray said he would continue to have treatment on the shoulder.
Earlier, world number one Serena Williams needed a shot of coffee to regain her best form during her opening match at the tournament.
Perked up by a cup of coffee at the end of the first set, Williams recovered from a disastrous start to defeat Flavia Pennetta as the United States beat Italy 3-0 in their Group A tie.
After Williams gave the Americans the lead, the towering John Isner then secured the tie with a grinding three-set win over Fabio Fognini.
Isner dropped the first set, but fought back to win 5-7, 7-5, 7-6 (7/4) in two hours and 27 minutes.
The Americans then survived two match points to claim the dead mixed doubles rubber in a match tie-break, 6-2, 2-6, 11-9.
Williams, who will be aiming for her 19th Grand Slam singles title at the Australian Open later this month, had her hands full with 12th-ranked Pennetta in the early stages of her first singles match of the new year.
Pennetta raced through the first set in just 19 minutes, winning 6-0 as a listless Williams made a string of unforced errors.
After the fifth game, a weary Williams asked an amused chair umpire if she was allowed to have an "espresso" coffee delivered to her courtside.
At the end of the set, Williams received the coffee and it had an immediate impact, as she broke the drought by winning the first game of the second set.
Although Pennetta made another two early breaks to lead 3-2 in the second set, Williams then kicked into gear, rattling off the last 10 games of the match in an early-season reminder of her brutal power.
The American won 0-6, 6-3, 6-0 and said she needed something to perk her up, having only arrived in Perth on Saturday.
The 33-year-old praised the "miracle" of coffee after the turnaround.
"I am a coffee drinker and I didn't have mine this morning and I was just feeling it so, I had to get some coffee in me," she said.
"I told them to just give me a shot of espresso. I asked if it was legal, I was like 'is it legal to have espresso' because I never did it before but I needed some espresso and I needed to wake up, it's the jet lag."Results from the mixed teams Hopman Cup at the Perth Arena on Monday.
Group B tie
Great Britain bt France 2-1
Men's singles: Andy Murray (GBR) bt Benoit Paire (FRA) 6-2, 7-5
Women's singles: Alize Cornet (FRA) bt Heather Watson (GBR) 6-2, 6-2
Mixed doubles: Watson/Murray (GBR) bt Cornet/Paire (FRA) 6-4, 2-6, 10-8 (match tiebreak)
Group A tie
United States bt Italy 3-0
Women's singles: Serena Williams (USA) bt Flavia Pennetta (ITA) 0-6, 6-3, 6-0
Men's singles: John Isner (USA) bt Fabio Fognini (ITA) 5-7, 7-5, 7-6 (7/4)
Mixed doubles: Williams/Isner (USA) bt Pennetta/Fognini (ITA) 6-2, 2-6, 11-9 (match tiebreak)