PERTH (AFP) - Agnieszka Radwanska led Poland to a win over the United States on Saturday, in their first victory at the mixed-team Hopman Cup in Australia.
The world No. 5 teamed up with Hopman debutant Jerzy Janowicz to beat the US pairing of Serena Williams and John Isner 2-1, atoning for the disappointment of losing last year's final to France.
Radwanska set up the win when she stunned a feisty Williams in the women's singles tie that opened the final, beating the world No. 1 for the first time in nine meetings.
Isner then levelled with a straight-set win over Janowicz, before the Poles clinched the title in a spirited mixed-doubles encounter.
It was a difficult night for Williams, who was aiming to become the first player to win three Hopman Cup titles.
Williams had a heated discussion with the chair umpire over a contentious point in the third set of the doubles and appeared to call the umpire a "liar" before the tournament referee came onto court to resolve the issue.
The 33-year-old then smashed her racquet when she missed a crucial shot on break point in the seventh game of the second set as the Poles pulled away to win the decider, 7-5, 6-3, and deny the US a record seventh title in the tournament's 27-year history.
Radwanska and team-mate Grzegorz Panfil were beaten by France's Alize Cornet and Jo-Wilfried Tsonga in the decider last year.
In the women's singles, Radwanska broke through for the first win of her career over Williams, 6-4, 6-7 (3-7), 6-1, in just over two hours.
Beaten by the American powerhouse in their previous eight meetings, in which Radwanska had only won a single set, she capitalised on the flood of unforced errors by Williams.
Radwanska tightened up when serving for the second set and allowed Williams to level the match.
However, the Pole regrouped in the third and secured the win when Williams made her 60th unforced error of the match to dump a forehand into the net.
The 25-year-old said the result was a great confidence boost ahead of the Australian Open in Melbourne later this month.
"I'm just really happy I played my best tennis today," she said.
"You know against Serena you never know and of course it doesn't matter what the score is, she's a great fighter.
"I'm just very happy that I could come back in that second set and play a good game in the third set."
Isner squared the ledger when he managed to down an inspired Janowicz in straight sets, 7-6 (12-10), 6-4 to level the tie, setting the scene for the doubles decider.
The Pole held two set points on his serve in the first set tie-break against Isner, but felt the pressure and squandered one with his first double fault of the match.
He then lost the second on a poorly advised drop shot, before serving his second double fault to hand Isner the set.
Isner made an early break in the second set and held onto that advantage.
Unfortunately for Williams, who was very inconsistent all tournament, her patchy form continued into the mixed doubles, where her misfiring serve helped the Poles climb back from being down a service break in the first set.