New York - Three-time defending champion Serena Williams launched her quest for a historic title Monday by overwhelming 86th-ranked Russian Vitalia Diatchenko and advancing to the second round of the US Open.
The world number one was a 6-0, 2-0 winner after only 30 minutes at Arthur Ashe Stadium when Diatchenko retired with a left foot injury, advancing Williams into a second-round match against Dutch qualifier Kiki Bertens.
"If I can just stay relaxed and stay in the points and stay calm and happy out there, I have to look at it as I have nothing to lose," Williams said.
The 33-year-old American chases the first calendar Grand Slam since Steffi Graf in 1988 and a 22nd career major title to match Graf's Open Era record, two shy of Australian Margaret Court's all-time mark.
Williams praised the loud New York crowd, which has adored her since she captured her first major title at the 1999 US Open as a teen prodigy.
"I felt the support and love on this journey and milestone I'm trying to take one match at a time," Williams said.
"I feel so good. I'm so ready. I'm at home, where it all began for me in '99. It all feels great."
Top-ranked Novak Djokovic and eighth seed Rafael Nadal also cruised into the second round on the men's side but Japanese fourth seed Kei Nishikori crashed out after his US Open runner-up effort last year.
Djokovic needed only one hour and 11 minutes to capture a 6-1, 6-1, 6-1 victory over Brazil's Joao Souza.
"There's something I love about number one for sure," said Djokovic, who plays Austrian Andreas Haider-Maurer next.
"Hopefully I can keep it up. If I can, I feel I have a really good chance against anybody."
Nadal, in his first US Open match since winning in 2013 after missing 2014 with an injury, avenged a loss last year at Basel to Croatian teen Borna Coric with a 6-3, 6-2, 4-6, 6-4 victory, booking a date with Argentina's Diego Schwartzman.
"I missed a lot this fantastic crowd that gave me unbelievable support," Nadal said. "Very happy to be back and be through."
Djokovic's highest-ranked possible semi-final foe had been Nishikori, but the Asian number one exited the US Open at the first match for the third time in five years as France's 41st-ranked Benoit Paire saved two match points to win 6-4, 3-6, 4-6, 7-6 (8/6), 6-4.
"To beat Nishikori, for me, it was impossible to imagine this," Paire said. "I'm really happy."
Paire, who had never before beaten a top-five foe, fired 21 aces to only three for Nishikori and blasted 64 winners, 30 more than Nishikori.
"He was very aggressive, so there were many rallies and it was tough to get rhythm," Nishikori said.
Nishikori led the tie-breaker 6-4 but swatted a forehand long, watched Paire smack two service winners and then Nishikori netted a forehand to force a fifth set.
Paire, who won his first ATP title last month at Bastad, broke for a 3-2 lead and held to the finish to win after three hours and 14 minutes.
Reigning champion Marin Cilic of Croatia won his opener 6-3, 7-6 (7/3), 7-6 (7/3) over Argentine qualifier Guido Pella.
"Defending a Grand Slam title for the first time for sure is something I will learn from," Cilic said.
Williams lost plenty of potential obstacles in her march to history on day one as top-10 women's seeds Ana Ivanovic, Karolina Pliskova and Carla Suarez Navarro exited with opening-match losses.
That left 12th seed Belinda Bencic - who ousted Bulgarian Sesil Karatancheva 6-1, 6-2 - as the top-rated foe in Williams' half of the draw. Williams, who lost to Bencic in the Toronto semi-finals, could see the Swiss teen again in a quarter-final.
Williams, who owns six US and Australian Open and Wimbledon titles plus three French Open crowns, won her 22nd US Open match in a row since her last loss, to Aussie Samantha Stosur in the 2011 final. Williams has won eight Slam titles since then.
Slovakia's 50th-ranked Dominika Cibulkova ousted seventh-seeded Ivanovic 6-3, 3-6, 6-3, delivering the Serb star's earliest US Open exit since 2009.
After the injury-forced withdrawal of Russian third seed Maria Sharapova, Ivanovic had been Williams' top-ranked rival in her half of the draw.
That status fell to Czech eighth seed Pliskova, who promptly lost to American Anna Tatishvili 6-2, 6-1, and then to 10th seed Suarez Navarro, who fell to Czech Denisa Allertova 6-1, 7-6 (7/5).
One Williams rival who advanced was her older sister Venus, a seven-time Grand Slam champion. The US 23rd seed outlasted Puerto Rico's Monica Puig 6-4, 6-7 (7/9), 6-3.
US Open results on Monday, the first day of the 2015 tournament at Flushing Meadows (x denotes seeded player):
Novak Djokovic (SRB x1) bt Joo Souza (BRA) 6-1, 6-1, 6-1
Andreas Haider-Maurer (AUT) bt Vasek Pospisil (CAN) 6-4, 3-6, 6-7 (0/7), 6-0, 6-1
Teimuraz Gabashvili (RUS) bt Pablo Andjar (ESP) 7-6 (8/6), 0-6, 4-6, 6-4 - retired
Andreas Seppi (ITA x25) bt Tommy Paul (USA) 6-4, 6-0, 7-5
Roberto Bautista (ESP x23) bt Pierre-Hugues Herbert (FRA) 6-3, 6-2, 7-6 (9/7)
Pablo Carreo-Busta (ESP) bt Jerzy Janowicz (POL) 6-3, 4-6, 6-2, 6-4
Ricardas Berankis (LTU) bt Joo Sousa (POR) 6-2, 6-2, 4-6, 2-6, 7-6 (7/4)
David Goffin (BEL x14) bt Simone Bolelli (ITA) 6-4, 6-1, 6-2
Milos Raonic (CAN x10) bt Tim Smyczek (USA) 6-4, 7-6 (10/8), 6-1
Fernando Verdasco (ESP) bt Tommy Haas (GER) 3-6, 6-1, 6-7 (3/7), 6-3, 6-1
Mardy Fish (USA) bt Marco Cecchinato (ITA) 6-7 (5/7), 6-3, 6-1, 6-3
Feliciano Lopez (ESP x18) bt Nikoloz Basilashvili (GEO) 7-6 (7/5), 6-1, 6-3
Fabio Fognini (ITA x32) bt Steve Johnson (USA) 2-6, 6-3, 6-4, 7-6 (7/2)
Pablo Cuevas (URU) bt Dudi Sela (ISR) 6-2, 3-6, 6-4, 6-1
Diego Schwartzman (ARG) bt Elias Ymer (SWE) 6-3, 6-2, 6-2
Rafael Nadal (ESP x8) bt Borna Coric (CRO) 6-3, 6-2, 4-6, 6-4
Benot Paire (FRA) bt Kei Nishikori (JPN x4) 6-4, 3-6, 4-6, 7-6 (8/6), 6-4
Marsel Ilhan (TUR) bt Radek Stepanek (CZE) 6-0, 2-6, 6-4, 3-2 - retired
Samuel Groth (AUS) bt Aleksandr Dolgopolov (UKR) 4-6, 6-1, 7-5 - retired
Tommy Robredo (ESP x26) bt Michael Berrer (GER) 6-2, 6-2, 6-4
Jo-Wilfried Tsonga (FRA x19) bt Jarkko Nieminen (FIN) 6-3, 6-1, 6-1
Marcel Granollers (ESP) bt Luks Lacko (SVK) 6-2, 6-3, 6-1
Sergiy Stakhovsky (UKR) bt John Millman (AUS) 6-1, 3-6, 7-6 (7/3), 6-4
Illya Marchenko (UKR) bt Gael Monfils (FRA x16) 2-6, 6-4, 5-0 - retired
Marin Cilic (CRO x9) bt Guido Pella (ARG) 6-3, 7-6 (7/3), 7-6 (7/3)
Evgeny Donskoy (RUS) bt Lucas Pouille (FRA) 6-2, 6-7 (3/7), 6-2, 6-4
Mikhail Kukushkin (KAZ) bt Lu Yen-Hsun (TPE) 6-3, 6-3, 3-0 - retired
Grigor Dimitrov (BUL x17) bt Matthew Ebden (AUS) 6-4, 6-2, 6-4
Jrmy Chardy (FRA x27) bt Ryan Shane (USA) 6-2, 6-1, 6-7 (6/8), 6-2
Martin Klizan (SVK) bt Florian Mayer (GER) 6-7 (5/7), 6-3, 6-3, 3-0 - retired
Filip Krajinovic (SRB) bt Alejandro Gonzlez (COL) 6-4, 6-0, 6-4
David Ferrer (ESP x7) bt Radu Albot (MDA) 4-6, 7-5, 6-1, 6-0
Serena Williams (USA) bt Vitalia Diatchenko (RUS) 6-0, 2-0 - retired
Kiki Bertens (NED) bt Mirjana Lucic-Baroni (CRO) 3-6, 6-4, 6-2
Bethanie Mattek-Sands (USA) bt Kateryna Kozlova (UKR) 6-4, 6-3
Coco Vandeweghe (USA) bt Sloane Stephens (USA x29) 6-4, 6-3
Madison Keys (USA x19) bt Klara Koukalova (CZE) 6-2, 6-4
Tereza Smitkov (CZE) bt Andreea Mitu (ROM) 7-6 (7/4), 6-2
Magda Linette (POL) bt Urszula Radwanska (POL) 7-6 (7/3), 6-1
Agnieszka Radwanska (POL x15) bt Katerina Siniakova (CZE) 6-2, 6-3
Belinda Bencic (SUI x12) bt Sesil Karatantcheva (BUL) 6-1, 6-2
Misaki Doi (JPN) bt Daniela Hantuchova (SVK) 6-3, 6-3
Irina Falconi (USA) bt Samantha Crawford (USA) 6-4, 6-2
Venus Williams (USA x23) bt Mnica Puig (PUR) 6-4, 6-7 (7/9), 6-3
Anastasia Pavlyuchenkova (RUS x31) bt Magdalna Rybrikov (SVK) 6-4, 7-5
Anett Kontaveit (EST) bt Casey Dellacqua (AUS) 7-5, 6-2
Madison Brengle (USA) bt Zheng Saisai (CHN) 6-2, 5-7, 7-5
Anna Tatishvili (USA) bt Karolna Plskov (CZE x8) 6-2, 6-1
Darya Kasatkina (RUS) bt Daria Gavrilova (AUS) 6-2, 4-6, 7-5
Ana Konjuh (CRO) bt Tatjana Malek (GER) 6-4, 6-4
Bojana Jovanovski (SRB) bt Lara Arruabarrena (ESP) 6-2, 6-2
Kristina Mladenovic (FRA) bt Svetlana Kuznetsova (RUS x30) 6-3, 7-5
Elina Svitolina (UKR x17) bt Elizaveta Kulichkova (RUS) 6-1, 6-4
Kaia Kanepi (EST) bt Anna-Lena Friedsam (GER) 6-1, 6-1
Lauren Davis (USA) bt Heather Watson (GBR) 7-6 (7/3), 7-6 (7/0)
Ekaterina Makarova (RUS x13) bt Teliana Pereira (BRA) 6-3, 6-3
Denisa Allertova (CZE) bt Carla Surez (ESP x10) 6-1, 7-6 (7/5)
Roberta Vinci (ITA) bt Vania King (USA) 6-4, 6-4
Mariana Duque (COL) bt Sofia Kenin (USA) 6-3, 6-1
Ocane Dodin (FRA) bt Jelena Jankovic (SRB x21) 2-6, 7-5, 6-3
Eugnie Bouchard (CAN x25) bt Alison Riske (USA) 6-4, 6-3
Polona Hercog (SLO) bt Zarina Diyas (KAZ) 6-2, 7-5
Jessica Pegula (USA) bt Alison Van Uytvanck (BEL) 7-5, 6-3
Dominika Cibulkova (SVK) bt Ana Ivanovic (SRB x7) 6-3, 3-6, 6-3