Basically AFL listed players need to have played 7 VFL games to qualify for the VFL finals. The first week of the finals though is open to all AFL players so that's why Howat played against Geelong.
The actual criteria is long and technical:
21. PARTICIPATION IN FINALS
21.1 Players who have not played at least one (AFL or VFL) Senior or Reserve match in the relevant season shall be ineligible to play in the Senior Grade Finals.
21.2 Players who have played with the AFL Senior team of any AFL Club after the 1st day of July in the relevant season shall be ineligible to play in the VFL Senior or VFL Reserve Grade Finals unless they have played a total of at least seven (7) Senior or Reserve VFL matches in the same season.
21.3 Players who have not played at least two (2) VFL Reserve Grade matches in the relevant season shall be ineligible to play in the VFL Reserve Grade Finals save where immediately prior to selection, a listed player has missed through injury, at least ten (10) consecutive home & away matches of the VFL football season and his club remains active in the senior VFL Finals series.
21.4 Players who have played in more than eight Senior VFL Grade matches shall not be eligible to play in Final Series matches of the VFL Reserve Grade unless they have played in at least six matches of the VFL Reserve Grade.
21.5 Notwithstanding the provisions of Rule 21 when a Club has each of its Senior Grade (AFL or VFL) and Reserve Grade (AFL or VFL) teams engaged on the same day, (or consecutive days) the selection of players in the two teams shall be unrestricted, provided a player has participated in at least one (AFL or VFL) Senior Grade or Reserve Grade match in that relevant season.
21.6 Notwithstanding the provisions of Rule 21 when an AFL Club is still qualified to participate in the AFL Finals Series, all such AFL Club listed players shall be eligible to be selected for a team participating in either the VFL Senior or VFL Reserve grade Finals Series game provided that such player has played at least 1 game in the VFL Senior Grade or missed through injury at least 8 consecutive Home and Away matches of either the AFL or VFL Season.
21.7 Not withstanding the provisions of Rule 21, a minimum of 10 VFL listed players must be selected in the VFL Senior finals team for all VFL Finals matches (excluding VFL Club(s) who do not field a VFL Reserve grade team).
21.8 Not withstanding the provisions of Rule 21.7, should additional AFL listed players qualify to participate in the VFL Final Series, all such AFL listed players will be eligible to be selected for a team participating in the VFL Reserve Grade Finals provided that player has played at least one game in the VFL Senior Grade or missed through injury at least 8 consecutive Home and Away matches of either the AFL or VFL Season.
21.9 Not withstanding the provisions of Rule 21, when an AFL Club is eliminated from the AFL Final Series on the same weekend as the VFL Grand Final, AFL listed players must qualify for selection under Regulation 21.2.
21.10 Not withstanding the provisions of Rule 21, for a VFL Club(s) who do not field a VFL Reserve Grade team in the competition, AFL listed players must qualify players under Regulation 21.2 and must have played not more than 12 AFL games to be eligible to play in VFL finals matches.
21.11 Not withstanding the provisions of Rule 21, for a VFL Club(s) who do not field a VFL Reserve Grade team in the competition, when an AFL Club has completed the AFL Home and Away season or is eliminated from the AFL Final Series, a minimum of 10 VFL listed players must be selected in the VFL Senior finals team for all VFL Finals matches. The balance of the 10 VFL listed players can comprise of AFL veterans listed and AFL rookie listed have qualified under Rule 21.10 and VFL listed players who have qualified under Rule 21.1.
