Kennett also said the team had been "outplayed and outcoached" by the Sydney Swans on Saturday.
The Hawks have had a rollercoaster year. They started the season poorly, winning just one of the first seven games before storming back into finals' contention on the back of seven consecutive victories.
But since round-17's draw with St Kilda, Hawthorn has been upset by Port Adelaide and the Swans, leaving it in danger of missing the finals for the second year running and the president clearly frustrated.
“Let me assure you there is absolutely no crisis at the club," Kennett wrote on Hawthorn's website. "In fact, the club is in a very good and healthy place. With one exception. We need to improve in the football department and on the field.
“It just may be that we are simply not good enough, and clearly we are not good enough to be in the top four. Now the question is being justifiably asked - are we good enough, do we want to be in the top eight?
“A premiership in 2008 and not make the top eight in two successive years? That would be a telling statistic.”
Kennett said he was set to write his latest letter to the members after the round-18 loss to Port Adelaide - which was 13th at the time - but he’d held off after he was accused by a senior player of being too quick to kick the team when it was down.
But after the side was comprehensively outplayed by the Swans, Kennett put pen to paper, saying optimism was fine but reality had to be faced.
He acknowledged that those he was taking aim at in the football department would not be happy with his spray.
“I know some of our players and coaches will be upset at me expressing the views I have in this letter to you today. But not to do so would be to spit in the face of the bleeding obvious.
“We can't run and hide forever. We can't make excuses. We are either good enough, committed enough, or we are not.”
