The New York Islanders star tied the single-season NHL record for goals by a rookie defenceman on Thursday.
Schaefer did so by potting his 23rd of the year against the Toronto Maple Leafs, matching the mark set by Brian Leetch in 1988-89.
The 2025 No. 1 overall pick already became the youngest defenceman to reach the 50-point mark in NHL history in March, doing so at 18 years, 195 days.
Schaefer now has 59 points on the season, as he has also dished 36 assists.
The Hamilton, Ont., native is second in rookie scoring, behind only Ivan Demidov.