A Roosters victory would make 37-year-old Daly Cherry-Evans the oldest premiership winner in 93 years.
He would also surpass Lote Tuqiri for the longest gap between titles.
Sunday's grand final against Newcastle will be Cherry-Evans' 379th and final NRL game. The Knights are chasing their first premiership in 25 years.
Kieran Foran was among the first to congratulate his former halves partner on reaching another grand final.
"I just said something along the lines of: 'It's been quite incredible what you've been able to achieve this year'," Foran told AAP.
"Because I just know how much this means to him on a far deeper level than what he talks about publicly."
Cherry-Evans won a premiership as a Manly rookie in 2011. He and Foran played together 190 times, including Manly's 2013 grand final defeat to the Roosters, when Cherry-Evans won the Clive Churchill Medal.
Cherry-Evans has said the intervening lean years made him appreciate reaching the finals.
"There were a couple of lean years there and it gives you a really strong appreciation for the times you do get to play in a finals series."
Foran said the pair had discussed the possibility of another grand final over coffee in recent years.
Cherry-Evans' move from Manly to the Roosters at the end of last year was a risk, Foran said, with pressure to deliver at his new club.
"He took a risk to say, 'I'm going to go somewhere else, and I'm going to back myself to play in another grand final'," Foran said.
Foran has admired Cherry-Evans' tenacity, his combination with Sam Walker and the fact he played every game this year.
Foran, appointed as Anthony Seibold's replacement at Manly, said Cherry-Evans would feel justified in leaving after helping the Roosters reach the grand final.
"But given what he's been able to achieve this year and what the team's been able to achieve, he'll feel justified in that decision."