Actually, Belgian co-commentator Steven Martens was comparing Kuznetsova's and Vaidisova's record in TBs when they started theirs.
I don't remember the exact numbers but he said:
Kuznetsova won about 50% of her TBs in her career
Vaidisova's record was far better (75% or more if my memory doesn't betray me, maybe someone can look it up - I'm too lazy at the moment) - so, in truth, she is more than capable of winning TBs, except at RG perhaps. - but don't forget that in 3 out of 4 her opponent was far more experienced than her - and at those moments experience counts more than ever.
Riding the 3AM Rollercoaster