according to Croatian media, Iva Majoli already traveled to USA and will help Donna prepare for the rest of US Open Series. article also mentioned the possibility of Majoli taking the role of Donna's permanent coach
Wozniacki has magnificent shotmaking if you ask me, but it's not the power kind of one. She has to rely on all court tactics to make effective her sweet topspin mix, while still able to hit pretty decent winners when she feels them, especially with the backhand. Despite not making many winners, she's still an agressive baseliner, and she doesn't only win matches by waiting the opponent's mistake, though she can do that at times also.
Well, she definitely needs to improve some things. Her serve has to go to another level I think. Fitness and movement too. But given her history it's not totally surprising that she has gotten into another little slump. Hopefully this time she'll get out of it a bit quicker than last time.
It also might be the case that Belinda is a difficult opponent for her.