The Vancouver Whitecaps gave 15-year-old Alphonso Davies a professional contract on Friday night and an MLS debut a day a later.
Davies, who already played for the Caps in four Canadian Championship games this year, entered Saturday's 2-2 draw against Orlando City in the 76th minute.
He is the first player to sign a pro deal from Vancouver's USL affiliate WFC2 and the third-youngest signing in MLS history at 15 years, 262 days.
Only D.C. United's Freddy Adu (14 years, 168 days) in 2004 and Toronto FC's Fuad Ibrahim (15 years, 130 days) were younger when they signed their MLS pro contracts.