Halifax are guaranteed a top four finish, and victory on Sunday would ensure they finish in the top three following last week’s 34-4 win at Keighley.
Harrison said: “We were exceptional in the first half against Keighley. Defensively we were very, very strong and we were fluent with the ball.
“We work extremely hard defensively. To win the Grand Final or go a long way in the play-offs you need to be strong defensively.
“If we go from now until the end of the season conceding one try a game, we’ve a good chance of winning it.”
Workington coach Gary Charlton will check on a number of players after a gruelling schedule that saw Town play seven games in 25 days.