BOSTON — Sometimes it’s hard to remember that Jayson Tatum only is 19 years old.

The Boston Celtics forward has exceeded expectations in his rookie season, and his performance in the first quarter against the Milwaukee Bucks on Monday proved to be one of his best showings yet.

Tatum was lights out in the opening 12 minutes at TD Garden, sinking all four of his 3-point attempts en route to 14 first-quarter points.

And the rookie joined one of the franchise’s best players in the record books in the process.

The C’s appear to have struck a gold mine with their No. 3 overall pick in this year’s draft.

Thumbnail photo via Winslow Townson/USA TODAY Sports Images