"This is an injury which could keep me out of the Australian Open".
As for the final, Kyrgios said he'd worked himself into the tournament and was ready to win a title with little more than a week to go before the Australian Open, the first major of the season.
Sunday was a charmed one for Davis Cup team members in Brisbane, with Kyrgios claiming his first ATP title on home soil and Australian doubles mainstay John Peers adding another title to his growing tally.
Kyrgios admitted after his quarter-final win over Alexandr Dolgopolov that he sometimes turns his talent on and off "like a tap".
He will take on world No.47 Harrison who ended Australian wildcard Alex de Minaur's giant killing run with a three set semi-final win on Saturday.
But the 22-year-old reckons there's a much bigger prize on offer - joining Hewitt on Brisbane's winners list four years after cheering him on to an upset victory over Roger Federer.
"It's huge for me. I love playing in front of you guys (Brisbane spectators) even though sometimes it might not seem like I do", said Kyrgios, who said he liked the idea of being on the Brisbane champions list with Lleyton Hewitt, the 2014 victor.
"I've obviously got one eye on it. and right now is the flawless time for us to win it".
"For me, that's just confidence not only mentally but physically as well, and battling and fighting hard", he said.
Australia has not won a Davis Cup since 2003, although came close a year ago in a 3-2 semi-final loss to the David Goffin-led Belgium on clay. "He had a great previous year beat me two times", Krygios said.
"It would be something great (to win one)". Kyrgios is hoping to improve on that after a confidence-boosting performance in Brisbane, where he beat defending champion and No. 3-ranked Grigor Dimitrov in the semifinals.
He played down any concerns regarding his strapped left knee on Sunday night, saying he was confident his body was ready for the grind of best-of-five set grand slam tennis in Melbourne.