Andy Murray will take on world number 104 Tennys Sandgren in his opening round.
Nadal and Federer have won a combined nine titles in 2017 and are ranked one and three in the world, respectively.
Three men can emerge from the final Grand Slam of 2017 at Flushing Meadows at the top of the ATP standings.
Federer has won five titles in 2017 including two Grand Slam titles - Australian Open and the Wimbledon.
Federer has been beaten just three times in 38 outings in 2017.
Nadal is returning to the top of the men's singles ranking for the first time since 6 July 2014.
Murray has not played since Wimbledon due to a hip injury.
Cristiano Ronaldo, Lionel Messi and Antonio Banderas took to social media to express their support for the victims.
The previous record was also in Montreal with 213,760 spectators.
Nadal will be confirmed as the world No1 when the rankings are recalibrated at the end of this week.
The 36-year-old suffered back problem in Rogers Cup final loss to Alexander Zverev.
Swiss star could become the oldest world number one ever if he wins the latest Masters 1000 event.
Both Federer and Nadal can become the new world number one depending on their results.
Federer and Nadal will battle for top spot in the men's singles rankings at this week's Cincinnati Masters.
Nadal exited the Rogers Cup after his third round loss to the Canadian.
Nadal can take over the top ranking from Murray by making the semi-finals at the Rogers Cup.
The 19-time grand slam champion wins opening match at Rogers Cup by beating Peter Polansky.
Three-time major champ now a big doubt for the US Open due to ongoing hip injury.
The Spaniard jokes "leave something for the young ones" as Federer prepares to return.
Two-year rankings would allow more players to take breaks and rest up.
Nadal can become world No1 if he makes the semi-finals at the Rogers Cup this week.
Nadal is on course to regain his world number one ranking at the Rogers Cup.