Baggies head coach Steve Clarke has confirmed Brown will be part of his squad to travel to Stamford Bridge and has a chance of appearing on the bench at the age of 16 years and 54 days.
Should the England Under-17 international get on to the pitch, he will surpass Fulham's Matthew Briggs' previous record - which was set in 2007 - by 11 days.
Albion needed permission to take Peterborough-born Brown out of school to train with the squad this week.
Injuries to several players and a doubt over the fitness of striker Shane Long have presented Brown with his opportunity.
The teenager has been part of Albion's academy set-up for the past three years and his performances for the under-18 and under-21 sides are understood to have attracted interest from Arsenal.
He is currently taking his GCSE exams but Albion's recently acquired status as a Category One academy means the club can take over young players' academic studies.
Brown would also be Albion's second youngest debutant - Frank Hodgetts was 16 years and 26 days when he appeared against Notts Country in 1940 in a war-time game.