The Kitchener, Ont., rookie will get his first start as part of the youngest opening unit in league history for the Washington Wizards on Saturday.
Riley, 19, will be joined by fellow Canadian Kyshawn George, 22, Bub Carrington and Alex Sarr, who are both 20, and 21-year-old A.J. Johnson for opening tip against the Charlotte Hornets.
Their average age of 20.64 years old breaks the record of 20.74 held by the Oklahoma City Thunder in a game from April 2021.
It marks a full embrace of the youth movement for the Wizards, who sit last in the Eastern Conference at 10-33 while riding an eight-game losing streak.
Riley, who was selected 21st overall in the 2025 draft, has appeared in 35 games for the team, averaging 14 minutes, 5.3 points and two rebounds per contest.
The Illinois alum was the first Canadian selected in his class after averaging 12.6 points, 4.1 rebounds and 2.2 assists per game while shooting 43.2 per cent from the field and 32.6 per cent from three-point range in his final NCAA season.