Kersten kicked four goals in the first half of the VFL preliminary final against Williamstown on Saturday to make a claim for the position left vacant by Chapman.
He was then rested for the second half, raising speculation he might be on standby.
Knights said Kersten was one of about eight Geelong players who could fill a void on Friday night if required.
"He's progressing well (but) still has a lot to work on as a young player. He's only in his second year. He's developing his game …is a beautiful kick (and) a lovely mark. His defensive pressure is getting better all the time," Knights said.
"He is still a work in progress but getting better and I am sure he would handle himself well in front of 90,000 people."
Knights said he expected Josh Caddy to be available for selection, having overcome a foot injury that kept him out of the semi-final against Port Adelaide.
Whether or not he would play in the AFL preliminary final or VFL Grand Final would be determined in the next 48 hours.
Knights said he did not expect to be making too many adjustments to the team, which goes into Sunday's VFL Grand Final as favourites.
Box Hill Hawks' Damian Carroll said he did not expect Hawthorn would rest any players from the VFL team if they happened to defeat Geelong on Friday night and made their way into the Grand Final.
"From our perspective Hawthorn has always wanted us to compete and compete hard and win and play with what we can. If there was a serious injury and we knew they were going to lose that player it might be something they would have to consider and that would obviously be fair enough," Carroll said.
The VFL Grand Final is at Etihad Stadium on Sunday at 2.15pm with the Geelong VFL team taking on the Box Hill Hawks.
