The American led the third set of her fourth-rounder 5-2, before injury gave way to tears and retirement.

But following a Paolini hold, Keys took the rare step of calling for the trainer and even leaving the court prior to her second attempt to close things out. Upon return, Keys wore tape on her left thigh, at which point the injury began to appear far more serious.

On the first point of the 5-4 game, Keys attempted to bail out of the rally with a drop shot. Paolini won that point. More notably, with Keys unable to push off her left leg, her second serve became a shadow of itself. At 15-30, a second serve clocked in at only 76 MPH, followed by another at 74 MPH, and then, at 30-40, a double-fault.

And though Keys won the first point of the 5-5 game courtesy of a clever drop shot-lob sequence, an ace from Paolini at 0-15 proved conclusive. After two hours and 23 minutes, Paolini had won, 6-3, 6-7 (6), 5-5, 15-all, retired.

“I was trying to fight every point because you never know here on grass if you are up or if you are down, every match can I think turn, you know, turn around,” said Paolini. “I was, like, just be focus and try to win points, to play points by point.”

But don’t think the drama was only confined to those final stages.

“It was a rollercoaster,” said Paolini in her post-match on-court interview.

Early on, the Italian had thoroughly dictated the tempo of just about every rally, requiring a mere 16 minutes to take a 4-0 first set lead and soon enough capture it, 6-3. Repeatedly, Keys lined backhands into the net and proved unable to dictate much of anything versus the enterprising and attentive Paolini. When Paolini broke Keys to start the second set, all seemed on course.

Then came a twist. Keys began to find her range. This was Keys at her best, a smothering flurry of depth, pace and accuracy that saw her race through five straight games and appear on the way to swiftly taking the match into a third set.

“Yeah, was a roller coaster because I think she’s playing unbelievable,” said Paolini. “I was doing more mistakes, her level was going up. It’s not easy to play against her because I think she’s one of the best players in the world. Of course, she’s hitting so fast.”