Wozniacki explains ongoing illness struggle

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The former world number one, who was diagnosed with rheumatoid arthritis before last year's US Open, pulled out of a second tournament in succession and had her place taken in the main draw by Polona Hercog, who was defeated by fellow lucky loser Stefanie Voegele 6-3 6-2.

Elise Mertens, seeded 16th, claimed the biggest title of her career at the Qatar Open at the weekend but she fell to a 5-7 6-4 7-5 loss against Zhu Lin on Monday.

Seeds Anett Kontaveit (15) and Julia Goerges (13) also suffered early exits.