Roger Federer delighted his home fans alongside Alexander Zverev, as the European pair saw off Shapovalov and Sock after a dramatic second set.
ATP Cup, the new world tennis team event, will feature 24 nations split into six groups across Sydney, Brisbane and Perth.
Sumit Nagal is yet to drop a set in the tournament and a win in the final will help him break into the top 150 in ATP rankings.
Rafael Nadal's latest coronation, his 19th Grand Slam title, reinforced the fact the slower courts of the US Open and his obliging knees have turned New York into a land of opportunity.
Roger Federer crashed out of the US Open after losing 6-3, 4-6, 6-3, 4-6, 2-6 to Grigor Dimitrov in quarter-finals on Wednesday.
Novak Djokovic received treatment before the start of the third set against Stan Wawrinka but soon threw in the towel, the 6th time he has retired at a Grand Slam tournament.
Roger Federer, trying to stretch his men's Grand Slam record title total to 21, advanced to a last-eight match up with Bulgaria's 78th-ranked Grigor Dimitrov.
Serena Williams continued her quest for a 24th career Grand Slam title to equal Margaret Court's all-time record by crushing Karolina Muchova 6-3, 6-2 in 74 minutes.
Novak Djokovic was treated for a sore left shoulder throughout his 6-4, 7-6 (7/3), 6-1 victory over Argentina's 56th-ranked Juan Ignacio Londero.
Sumit Nagal said qualifying for a hard court Grand Slam main draw was all the more pleasing because he spent an entire year competing on red dirt.
Sumit Nagal managed to take a set off Roger Federer in a US Open first-round clash.
Sumit Nagal managed to get a set off Roger Federer in their US Open first-round contest on Monday before the Swiss star won the next three sets.
Sumit Nagal made Roger Federer toil in the first round match at the US Open, managing to even take a set off the Swiss great.
Roger Federer, 20-time Grand Slam champion, defeated India's Sumit Nagal in the first round of the US Open.
Novak Djokovic takes inspiration from talk he could pass Roger Federer for the all-time record total of men's Grand Slam singles titles.
Sumit Nagal, ranked 190 in the world, will face 20-time Grand Slam champion Roger Federer at US Open's showpiece court, the Arthur Ashe Stadium, in the first round.
Former world number one Roger Federer, seeking a 21st Grand Slam crown, is seeded third for the tournament.
Controversy has arisen over the past months concerning various issues, with ATP Council president Novak Djokovic often on the opposite side of discussions from Rafael Nadal and Roger Federer.