She doesn't seem to hit harder than the other big hitters. I think people like Tracey see Maria as the biggest hitter and when someone out plays her it must be because they hit harder.
That's the Beauty Petra has, easy power. She doesn't swing hard, grunt or take wild swings, but she'll still pound her ground strokes 10-13mph more than your favorite ball basher during a match, and be able to hit a frozen rope winner from anywhere on or off the court from either wing in a blink.
Mary Joe Fernandez said "she hits the ball harder than anyone I've ever seen". Lindsay Davenport said " Stunning. I can see why people compare her to me, she's one of the best ball strikers I've ever seen". And she did have the highest ground stroke mph avg throughout the entire Wimby tournament according to their statistics. Need I say more?
To be quite honest, I haven't seen anyone be able to hit winners like she does from anywhere on the court from either wing. So from that perspective I can see her ushering in a new form of power tennis (at least in Tracy's mind) along with her aggression, net play, slice backhand, tricky serves and drop shots.
As a matter of fact I and many people who became Kvitova fans, became fans cause we've never seen people do what she does on the tennis court as consistently as she does, and that's hit winners from any position from anywhere on the court. She has great power, technique and execution. That should be clear to see, and one of the things that separates her from the Masha's and everyone else on tour.
But who care's what Tracy Austin thinks anyway?