With Rafael Nadal beaten earlier in the day, Roger Federer came to Europe's rescue to win the inaugural Laver Cup.
Damir Dzumhur came from behind to inflict a second St Petersburg Open final defeat on Fabio Fognini.
Peter Gojowczyk saw off Benoit Paire 7-5 6-2 to win his first ATP World Tour title in Metz.
For the eighth successive match Kristina Mladenovic suffered a straight-sets defeat on the opening day of the Wuhan Open on Sunday.
French Open champion Jelena Ostapenko sealed her second career title at the Korea Open with a three-set victory over Beatriz Haddad Maia.
Without a win in six WTA finals in 2017, Caroline Wozniacki captured her first championship of the season on Sunday.
Roger Federer and Rafael Nadal played doubles together at the Laver Cup on Saturday, but do not expect it to happen again.
Jack Sock and Sam Querrey put up a valiant effort against two of the game's greats, but were no match for Roger Federer and Rafael Nadal.
The Moselle Open final will see home favourite Benoit Paire take on German Peter Gojowczyk on Sunday.
Roberto Bautista Agut fell short at the semi-final stage once again in St Petersburg as Fabio Fognini and Damir Dzumhur reached the final.
Rafael Nadal and Tomas Berdych's defeat in doubles was the only loss of the day for Europe in the Laver Cup.
Caroline Wozniacki and Anastasia Pavlyuchenkova will meet in the Tokyo Open final after contrasting last-four wins.
While Jelena Ostapenko made serene progress in Seoul, fellow top-three seeds Kiki Bertens and Kristyna Pliskova suffered defeats.
Former champion Mikhail Youzhny made a winning start to his latest quest for a second St. Petersburg Open crown.
Seeking a fourth appearance in the final of the ATP Moselle Open, Gilles Simon made a solid start with a 6-3 6-0 win over Andreas Seppi.
Top seed Peng Shuai saved 10 break points in the deciding set against Ons Jabeur to progress at the Guangzhou Open.
Fourth seed Adrian Mannarino bid an early exit at the St Petersburg Open as Liam Broady's best run continued in emphatic fashion.
Denis Istomin produced an early shock at the Moselle Open as he dumped out sixth seed Richard Gasquet in the first round.
Garbine Muguruza put on an exhibition in the second set after being tested in the first by Monica Puig in Tokyo.