Thank you Vika
People on this board use the word "choke" too loosely. It was unrealistic to expect Petra to play at that level the entire match, when most are even agreeing it's the best she's played against a top player since YEC '11. Players like Kvitova who go for so much on every shot are always going to be in danger of playing a loose game. Besides, heading into the service game at 4-2, Petra was already serving at 44% for the set, and that's including all the games she won to go up 4-1 in the first place.
Just pulled up the match on YT, and help me out here: Where is the choke?
Serena's 4-1 service game, point by point
Baseline rally #1, Kvitova hits a winner. 0-15.
Baseline rally #2, Kvitova hits an error. 15-15.
Baseline rally #3, Kvitova hits an error. 30-15.
Serena hits an unreturnable 1st serve. 40-15.
Serena's big serve sets up a forehand putaway. Game Serena.
Petra's 4-2 service game, point by point:
Serena draws Kvitova out wide forcing a FH error. 0-15.
Serena nets a ROS. 15-15.
Serena's deep ROS draws an error. 15-30.
Kvitova's great first serve sets up a FH putaway. 30-30.
Serena's deep ROS sets up a FH winner. 30-40.
Kvitova's DF. Game Serena.
Similar story in the next game, went to deuce but Serena finally found some first serves when she needed them, and after that it was (in hindsight) a formality. I knew right away that if Kvitova wanted to win this match she would have had to win that game at 4-2, but she didn't, and she paid. Hopefully she'll take this as a learning experience, but calling it a "choke" just screams someone who wasn't paying attention to the match.
Maybe what you interpret as choke is simply not being clutch. Kvitova is a player of the type that can outplay anyone, but is rarely the one I'll put my money one when it gets down to the wire, 5-5 30-30 in a deciding set.