It has been a breakthrough season for Southern California's Schauffele, who triumphed at this year's PGA Championship and British Open and is ranked a career-best second in the world.
Australia's Day meanwhile is eager to improve on his disappointing 5-11-4 record across four prior Presidents Cup appearances and will look to get a lift from the big-hitting South Korean An.
US captain Jim Furyk selected Collin Morikawa and Sahith Theegala for the second match and International Team captain Mike Weir countered with a pair of Australians in Adam Scott and Min Woo Lee.
World number one Scottie Scheffler and fellow American Russell Henley will face the South Korean duo of Im Sung-jae and Tom Kim in the third match of the day.
Canadian Taylor Pendrith will no doubt receive an enthusiastic welcome from the galleries at Royal Montreal Golf Club when he and South Africa's Christiaan Bezuidenhout take on Wyndham Clark and Keegan Bradley in the fourth match.
The first day of the three-day competition will conclude with Patrick Cantlay and Sam Burns battling Japan's Hideki Matsuyama and Canada's Corey Conners.
The US has dominated the biennial competition behind a 12-1-1 record and are once again the heavy favourites despite going up against a more experienced International Team.
The Internationals are returning eight players from their 2022 squad to the 12-player roster in the hope of ending a Presidents Cup drought that stretches back to their lone victory at Royal Melbourne in 1998.
The US has seen more turnover but boasts five of the top 10 players in the world and all 12 members are ranked inside the top 25 while the International Team's highest-ranked player is world number seven Matsuyama.