Diesel Hagan could become the first NRL Grand Final debutant since Eddie Lockhart in 1936, 90 years ago.
Phoenix Crossland's suspension has opened a place for Hagan on Newcastle's six-man bench.
"Diesel Hagan will be in the six-man bench," Knights coach Justin Holbrook confirmed on Saturday morning.
Holbrook praised Hagan's performances for New South Wales Under-19s, SG Ball and NSW Cup.
"He's a great young player. He played (for) New South Wales Under-19s this year, got Player of the Match and was their captain.
"Had a great year in SG Ball and played really well in NSW Cup. He's ready.
"Like a lot of young guys now, he's keen and ready to go.
Hagan's rise follows a difficult period in which he struggled to secure a place in Newcastle's Under-19s and managed only a couple of SG Ball games last year.
"It's definitely been a rollercoaster ride for him," his father Ben told foxsports.com.au.
"Last year he was struggling to make their SG Ball side. He only had a couple of games and then this year he has done pretty well."