London - Colourful US star Bethanie Mattek-Sands suffered an horrific knee injury at Wimbledon on Thursday which left her screaming in pain and heartbreakingly pleading for help.
The distressing drama on Court 17, where the 32-year-old lay stricken for at least 20 minutes, pushed the title campaigns of Novak Djokovic and Roger Federer onto the sidelines.
"Please help me! Please! Please!" screamed Mattek-Sands as she clutched her right knee after collapsing running to the net in the first point of the deciding set against Romania's Sorana Cirstea.
The women's tour said Mattek-Sands had suffered a serious knee injury.
"It is an acute knee injury and she has gone straight to hospital," the WTA Insider tweeted.
Mattek-Sands's husband Justin tried to console his wife as medics arrived, while Cirstea, who rushed over the net to help, was visibly distraught.
After lying prone on the ground screaming in pain as she waiting for medical assistance, Mattek-Sands was eventually stretchered away.
Her doubles partner, Lucie Safarova, with whom she shares the world number one ranking as well as four Grand Slam titles, also arrived at the scene in tears.
The terrible scenes on Court 17 dominated the fouth day of the tournament.
Earlier Novak Djokovic shrugged off sweltering 30-degree heat to breeze past outclassed Adam Pavlasek 6-2, 6-2, 6-1 and reach the third round.
The three-time champion brushed aside the 136rd-ranked Czech on Court One to make the last-32 for the ninth year in succession.
Djokovic, the second seed whose shock third round loss to Sam Querrey at Wimbledon 12 months ago precipitated a worrying decline in form, will next face Ernests Gulbis.
"It was a very warm day, it wasn't easy to play point after point and some long rallies," said Djokovic as his comfortable Wimbledon continued following a first round in which opponent Martin Klizan had retired hurt after just 40 minutes.
"But overall, from the very beginning I managed to impose my own rhythm and play the game I intended to play."
Gulbis sprang a Wimbledon surprise as the world number 589 defeated former US Open champion Juan Martin del Potro 6-4, 6-4, 7-6 (7/3).
The 28-year-old Latvian was ranked in the top 10 in 2014 -- the year he beat Federer en route to the French Open semi-finals.
Since then, Gulbis has slumped badly and his Wimbledon opening round win over Victor Estrella, was his first on tour in 13 months, a decline which has seen his ranking crash to his lowest position in 12 years.
Bulgarian 13th seed Grigor Dimitrov, a semi-finalist in 2014, saw off Cypriot veteran Marcos Baghdatis 6-3, 6-2, 6-1 while pint-sized Dudi Sela stunned giant American John Isner 6-7 (5/7), 7-6 (7/5), 5-7, 7-6 (7/5), 6-3.
Bernard Tomic may have been knocked out but the Australian was still making waves on Thursday when he was fined $15,000 after claiming he was "bored" during his lacklustre defeat to Mischa Zverev.
Tomic, who was accused of "unsportsmanlike behaviour" had also admitted he called for the trainer even though he was not injured to try to disrupt his opponent's momentum.
Russia's Daniil Medvedev was slapped with a $14,500 fine after a series of disputes with umpire Mariana Alves during his five-set loss to Ruben Bemelmans in the second round.
Medvedev ended the match by throwing coins in the direction of umpire's chair although he insisted the bizarre gesture was not meant to imply that the official was corrupt.
Later Thursday, third seed Federer was to continue his campaign for a record eighth Wimbledon title against world number 79 Dusan Lajovic.
Women's top seed Angelique Kerber, the runner-up to Serena Williams in 2016, tackles Belgium's 88th-ranked Kirsten Flipkens, whose best performance at the majors came at Wimbledon in 2013 when she made the semi-finals.
Czech third seed Karolina Pliskova hopes to make the last-32 for the first time, but she faces a tough test of her grass court credentials against Magdalena Rybarikova of Slovakia.
Former US and French Open champion Svetlana Kuznetsova, seeded seven, took her career record over fellow Russian Ekaterina Makarova to 7-1 with a 6-0, 7-5 win.
Kuznetsova next faces Slovenia's world number 265th Polona Hercog, who reached the third round at a Slam for the first time since 2010 with a 6-7 (2/7), 6-2, 6-2 win over Varvara Lepchenko of the United States.
Agnieszka Radwanska, the 2012 runner-up, saved two match points to see off Christina McHale 5-7, 7-6 (9/7), 6-3.
Wimbledon results on Thursday, the fourth day of the 2017 championships at the All England Club (x denotes seeding):
Grigor Dimitrov (BUL x13) bt Marcos Baghdatis (CYP) 6-3, 6-2, 6-1
Dudi Sela (ISR) bt John Isner (USA x23) 6-7 (5/7), 7-6 (7/5), 5-7, 7-6 (7/5), 6-3
Mischa Zverev (GER x27) bt Mikhail Kukushkin (KAZ) 6-1, 6-2, 2-6, 3-6, 6-4
David Ferrer (ESP) bt Steve Darcis (BEL) 3-0 -- retired
Gael Monfils (FRA x15) bt Kyle Edmund (GBR) 7-6 (7/1), 6-4, 6-4
Ernests Gulbis (LAT) bt Juan Martn Del Potro (ARG x29) 6-4, 6-4, 7-6 (7/3)
Novak Djokovic (SRB x2) bt Adam Pavlsek (CZE) 6-2, 6-2, 6-1
Polona Hercog (SLO) bt Varvara Lepchenko (USA) 6-7 (2/7), 6-2, 6-2
Svetlana Kuznetsova (RUS x7) bt Ekaterina Makarova (RUS) 6-0, 7-5
Lesya Tsurenko (UKR) bt Viktorija Golubic (SUI) 6-1, 2-6, 6-3
Coco Vandeweghe (USA x24) bt Tatjana Malek (GER) 6-4, 6-2