The former Manchester United midfielder, who spent a season with the Scottish Premier League side before retiring in 2006, blasted his former employers for their capitulation and, well, just about everything else really.
Keane believes it’s imperative that Celtic change their whole mindset, or else they’ll continue to be Champions League whipping boys.
Article continues below
The ITV Sport pundit was also infuriated that Celtic celebrated reaching the group stages following their two-legged victory over Hapoel Beer Sheva.
This two-minute rant was arguably one of Keane’s best - and there have been some crackers in recent years - so sit back, grab your popcorn and scroll down to read the quotes and watch the video.
Article continues below
Keane's epic rant on Celtic
“On one hand, we’re being told Celtic are a great club - great traditions, great history - and they go and lose 7-0 to Barcelona,” Keane began. “People almost say ‘these things happen’ and it’s acceptable.
“You spoke about the game against Rangers, they won 5-1, one of the worst Rangers teams I’ve seen in a long time.
“I think the idea that they were tired…” Keane can then be seen shaking his head in disagreement.
“They need to do a lot better in Europe - easier said than done, of course - but they were even poor in the qualifying games,” the Irishman continued. “They scraped through.
“I think their whole mindset has to change, don’t accept being the whipping boys in Europe.
“Celtic are a huge club and need to do much better.
“Even when they qualified for this group, their celebrations were well over the top. I thought they actually won the competition, people were hugging each other.”
“I appreciate that this group’s difficult because of Barcelona and Man City but over the past few years they’ve struggled. Lesser teams than Celtic have done well in Europe.”
Lee Dixon then argued that while Celtic might be a great club, they don’t possess a great team at this moment in time.
But Keane, resuming his rant, added: “A lot of these players are international players. It’s not Altrincham, it’s Celtic.”
After having another pop at his old club for celebrating qualification through to the group stages, Dixon put his arm around Keane and said: “Don’t worry, Arsenal are on next.”
This lightened the mood.
Video: Keane's rant in all its glory
Here’s how Twitter reacted to Keane’s rant…
Is Roy Keane right about Celtic? Have your say by leaving a comment below.
Do YOU want to write for GiveMeSport? Get started today by signing-up and submitting an article HERE: http://gms.to/writeforgms