Re: ~Petra Martic~
^^ Yeah, I also thought she'll play doubles last week, but it turns out it was a good choice to play only singles cause she was finding some great form.
Maybe they wanted to give her some extra warm-up time before big events by playing this week, but didn't want to drain her energy levels too much after that sickness (maybe it was something like a stomach virus, cause she's already back in action), so signed her up only for doubles. It's 4 matches at most, and they're not as long and exhausting as singles might be, so it's a safer bet. Also, she's not defending any doubles points until early April, so there's no real risk in terms of ranking.
Anyway, good luck girls!