Maria Sharapova made it a remarkable 20 victories from 23 grand slam quarter-finals but was pushed all the way at Wimbledon on Tuesday by feisty American Coco Vandeweghe before emerging a 6-3, 6-7(3), 6-2 winner.
The Russian fourth seed, Wimbledon champion as a 17-year-old in 2004 but a finalist only once since, had not dropped a set in this year's tournament coming into the last-eight contest.
However, after a relatively untroubled first set on Centre Court, she lost a hugely entertaining second as the two identikit 6ft-plus blondes with matching white visors slugged it out.
Vandeweghe, the only unseeded player in the last eight, showed plenty of grit, not least when breaking as Sharapova served for the match at 5-4 in the second set, whipping up Centre Court crowd in the process.
Sharapova then displayed her own fighting spirit when, despite again struggling with her serve, she twice saved set point before Vandeweghe's fearless deep hitting earned her the tiebreak and dreams of an upset victory.
In the final set Sharapova quickly seemed to take control with a break in the second game to race to a 3-0 lead but Vandeweghe refused to lay down or ease off and broke back to trail 3-2, again urging the crowd to get behind her as she marched back to her chair.
Sharapova had struggled for consistency all day but put together a run of aggressive, accurate returns together to break again for a 4-2 lead and then landed a rare ace to finish off her next service game to make it 5-2.
This time there was no coming back as Sharapova then broke again to take the match and set up a semi-final against either top seed Serena Williams or Victoria Azarenka, who were meeting on Centre Court later on Tuesday.
"I was pretty dominant in the first and early in the second set but things slipped away," said the five-times Grand Slam champion.
"She's playing with a lot of confidence but I really regrouped in the third.
"You have to give everything you have on a special occasion on a special court.
"It's been a while since I've been at the semi-final stage (at Wimbledon) so I'm really happy."
Serena overpowers Azarenka to reach semi-finals
Top seed Serena Williams overpowered Victoria Azarenka in an absorbing Wimbledon quarter-final on Tuesday, recovering from a set down to win 3-6, 6-2, 6-3.
The American, who will face Russia's Maria Sharapova in the semi-finals, is two wins away from holding all four grand slam titles concurrently -- the so-called Serena Slam she also achieved in 2002-03.
The 33-year-old was second best in the first set against the Belarussian former world number one on Centre Court, but she found an extra gear and dominated thereafter.
Three consecutive aces at 4-2 in the third set moved her to within a game of victory and although 23rd seed Azarenka hung on and threatened to break back, Williams would not be denied and stayed on course for a 21st Grand Slam title.
"It was fun out there and I saw Victoria smiling as well, we both really enjoyed it," five-times Wimbledon champion Williams, who has won 26 Grand Slam matches in a row, said in a TV interview.
Radwanska's grasscourt pedigree helps her reach semis
Agnieszka Radwanska made her wealth of grasscourt experience count as she dispatched American hope Madison Keys 7-6(3), 3-6, 6-3 to reach the Wimbledon semi-finals for the third time in four years.
The 2012 runner-up, who at 13 is the highest seed left in the bottom half of the draw, needed six set points to seal the first set while the second set slipped from her grasp after a bouncing net cord handed her 20-year-old rival a break in the eighth game.
Keys, one of three Americans to reach the women's quarter-finals along with world number one Serena Williams and Coco Vandeweghe, produced a 106mph thunderbolt to draw level.
That was one of 12 aces she fired down on Tuesday which prompted John McEnroe to observe: "That serve of hers is such a big weapon. It can save her".
However, being the tournament's leading ace lady -- with a total of 59 -- could not carry her over the finishing line.
Poland's Radwanska inched closer to victory by breaking in the eighth game of the decider and finished Keys off with a forehand winner.
She will meet Garbine Muguruza in Thursday's semi-final.
Muguruza finds her grasscourt groove to reach Wimbledon semis
Garbine Muguruza's new-found love-affair with grass blossomed further on Tuesday as she became the first Spanish woman in 18 years to reach the Wimbledon semi-finals with a 7-5, 6-3 win over Timea Bacsinszky.
The 21-year-old, who took instant dislike to the lush green surface after losing her first match on it three years ago in Birmingham, found her comfort zone to outwit Bacsinszky.
Muguruza, who was three years old when fellow Spaniard Aranxta-Sanchez Vicario reached the last four in 1997, pocketed the first set when her Swiss rival whipped a forehand wide.
The 20th seed kept up the momentum in the second to reach her first grand slam semi.
After watching 15th seed Bacsinszky roll the ball into the net on matchpoint, Muguruza collapsed on to her back before getting back up to bounce around court in joy.
She will next face either 2012 runner-up Agnieszka Radwanska, who at 13 is the highest seed left in the bottom half of the draw, or American Madison Keys.