Madrid woe for Wozniacki, sluggish Serena through
Caroline Wozniacki was shocked in the first round of the Madrid Open but Serena Williams managed to avoid her own upset as the tournament entered its second day.
England's Laura Robson got off to a winning start on Saturday but Wozniacki was caught cold 24 hours later as Yaroslava Shvedova triumphed 6-2 6-4 at La Caja Majica.
Ranked 25 places higher in the world rankings, world No. 10 Wozniacki was immediately made to feel uncomfortable by Shvedova, who broke three times in the first set.
The score reflected a tighter second stanza but Wozniacki was only kept alive by seven double-faults from her rival. Shvedova created 11 break chances in the second set alone, converting two en route to a shock victory.
Defending champion Serena Williams made a stuttering start to the defence of her crown, serving poorly but ultimately recording a 7-6(5) 6-1 triumph over Yulia Putintseva. Victory came in an hour and 37 minutes.
Williams was broken in the opening game by the world No. 88, but quickly levelled in the sixth. The American's serve was a mess in the first set, with only 32 per cent of first deliveries finding their target at one stage, but she edged the tiebreaker 7-5 to grab control of the match.
Armed with the lead, Williams shared three breaks of serve with Putintseva at the start of the second, two falling in the world No. 1's favour. She then found a third consecutive break of the Putintseva delivery to set up victory, before another clinched her spot in round two.
Elsewhere, sixth seed Angelique Kerber was a 3-6 6-3 6-2 winner over Su-wei Hsieh, 14th seed Marion Bartoli led 6-3 3-0 when Elena Vesnina retired, 15th seed Dominika Cibulkova beat Lesia Tsurenko 6-3 6-2, and No. 4 seed Agnieszka Radwanska overcame Tsvetana Pironkova 6-2 6-4.
Other notable results saw eighth seed Petra Kvitova come from a set down to beat Yanina Wickmayer 4-6 7-5 6-4, and former world No. 1 Ana Ivanovic survive a gruelling encounter against Bethanie Mattek-Sands 6-7(10) 6-3 6-2.