Forssell scored 17 times for Birmingham in the Premier League in 2003-04.
He told The Sun: "I'm not worried that Teemu will break my record because I know for sure that it will happen.
"Teemu will score at least 18 goals this season. I said it before the start of the season. I believed in him all the time.
"This is a fantastic thing for the whole of Finnish football. The game in our country has had challenging years but Teemu has shown what hard work can do.
"I hope every young footballer in this country will follow suit.
"It was an awesome accomplishment to score a hat-trick. I was like a fan and shouting at the TV. They were world-class goals."