Kennett told Melbourne radio station 3AW on Monday night that Hawthorn's seven-point loss to Geelong was a "disgrace" and symptomatic of a stale coaching structure that had him fearing for the Hawks' 2013 season already.
"From our side … it's time to review the coaching," Kennett said.
"The reality is we lost in 2011 in the preliminary final when we were well ahead. We failed to flood the backline.
"Last year I think we made a terrible decision when we played our captain Luke Hodge when he clearly wasn't fit and that to me is an absolute no no in a Grand Final.
"You can't go into that sort of match carrying people and today unfortunately we were outplayed and outcoached and unless there are some fundamental changes there I fear for our season.
"I know that's a big call early on, but I think we lost today in the same way we've lost to Geelong every time in the last (10) home and away games. We often start well and then we fail to deliver, and today our second half was a disgrace."
Clarkson is contracted at Hawthorn until the end of next season, but Kennett said he should accept responsibility for the Hawks' failure to add to their 2008 premiership despite boasting one of the best lists in the competition.
"I think Alastair is the head coach, he's got to accept responsibility for the failures in the last few years and particularly the way we conducted ourselves in the second two quarters (today)," Kennett said.
"They played well in the first half and then we let Geelong get away from us. We didn't man up. I couldn't see any fundamental changes in positions or tactics and you can't just continue to play on the hope that the side is going to do better.
"You've got to actually be more aggressive and you've got to be more proactive."
Kennett acknowledged Clarkson's "wonderful good personal values" and "great service" since taking the Hawks' coaching reins in 2005, but said he'd passed his use-by date.
"There was an excuse in 2009 for our performance because of injury, but 2010, 2011, 2012 we have underperformed and someone has to accept responsibility for that."
Kennett said he had "no doubt" Hawthorn's board would stick with Clarkson as coach this season, but believed it should look to replace Clarkson with a "hungry" assistant coach.
"I think we need to introduce a freshness at the club that doesn't exist at the moment because so many of the personnel have been there now for a number of years," Kennett said.
"So the senior players have been listening to the same voice for too long."
Nick Bowen covers Hawthorn news for AFL.com.au. Follow him on Twitter: @AFL_Nick
