Novak Djokovic and Roger Federer will make late summer hardcourt starts next week as the ATP and WTA Cincinnati Masters gets underway with all major names set to compete.
Along to give his resurfaced right hip a test after seven months of singles inactivity will be two-time champion Andy Murray, with the world number 325 entered on a wild card.
British three-time Grand Slam champion Murray's most recent singles match was a January first-round Australian Open loss, after which the Scotsman tearfully said his career might be over after playing and losing in severe hip pain.
He then underwent a successful hip surgery that has given his career a second chance at age 32.
Murray, a 2008 and 2011 Cincinnati champion, will open in the first round against France's Richard Gasquet, whom he leads 8-3 in their personal rivalry, taking their past three meetings dating to 2015 and 2016.
Federer, who turned 38 on Thursday, will need to lift his game immediately as he prepares for the US Open.
Federer has claimed the Cincinnati trophy seven times, most recently in 2015.
The icon with 20 Grand Slam singles titles has been holding off Djokovic and Nadal, who continue to close in on his record with 16 and 18 titles respectively.
Top seed Djokovic and number three Federer will both be playing for the first time since their Wimbledon final, won by the Serb after Federer held two match points.
Nadal takes the second seeding after a standout week in Montreal.
The Spaniard called Murray's return "good for the sport," suggesting the decision shows the 32-year-old feels healthy enough to compete at the top level.
Fourth seed Dominic Thiem will hope to keep lifting his hardcourt form after reaching the Montreal quarter-finals. Greek fifth seed Stefanos Tsitsipas will need to quickly improve after losing early in Canada.
Japan's Kei Nishikori take the fifth seeding ahead of Montreal quarter-finalist Alexander Zverev and Russian Karen Khachanov.
South African Kevin Anderson, the ATP number 10 who has not played since Wimbledon due to injury, is missing the US Open tuneup.
On the women's side, Australian Ashleigh Barty, who lost the top ranking with a first-match exit in Toronto, is seeded atop the table followed by double Grand Slam champion Naomi Osaka of Japan.
Czech Karolina Pliskova, the 2016 winner, is third ahead of Romania's Simona Halep and holder Kiki Bertens of the Netherlands.
Halep is dealing with an Achilles tendon injury after managing to play only one set in the Toronto quarters.
Serena Williams, a 23-time Grand Slam singkes winner, hopes to continue her fightback to match fitness, which was on solid display in a victory Friday over Osaka in a rematch of their 2018 US Open final.
The 37-year-old American will begin her campaign against a qualifier.
After losing the Wimbledon final against Halep, Williams is keeping her hopes toned down.
"I go into every match thinking I can do it, but sometimes that doesn't happen," she said. "Overall I just come and do the best I can."
Bertens could play Venus Williams in the second round if the veteran gets past a qualifier in her opening match.
Novak Djokovic (SRB x1)
Rafael Nadal (ESP x2)
Roger Federer (SUI x3)
Dominic Thiem (AUT x4)
Stefanos Tsitsipas (GRE x5)
Kei Nishikori (JPN x6)
Alexander Zverev (GER x7)
Karen Khachanov (RUS x8)
Daniil Medvedev (RUS x9)
Fabio Fognini (ITA x10)
Roberto Bautista Agut (ESP x11)
Borna Coric (CRO x12)
John Isner (USA x13)
Marin Cilic (CRO x14)
Nikoloz Basilashvili (GEO x15)
David Goffin (BEL x16)
Ashleigh Barty (AUS x1)
Naomi Osaka (JPN x2)
Karolina Pliskova (CZE x3)
Simona Halep (ROM x4)
Kiki Bertens (NED x5)
Petra Kvitova (CZE x6)
Elina Svitolina (UKR x7)
Sloane Stephens (USA x8)
Aryna Sabalenka (BLR x9)
Serena Williams (USA x10)
Anastasija Sevastova (LAT x11)
Belinda Bencic (SUI x12)
Angelique Kerber (GER x13)
Johann Konta (GBR x14)
Wang Qiang (CHN x15)
Madison Keys (USA x16)