United slipped to their third loss in the Premier League on Sunday as Pierre Emerick-Aubameyang’s penalty sealed a 1-0 win for Mikel Arteta’s side at Old Trafford.
Cavani, who joined on a free transfer from Paris Saint-Germain on deadline day, was brought on with 15 minutes remaining as United pushed for an equaliser.
And Keane was furious with the Uruguayan striker for his half-hearted preparations on the touchline.
The former United captain also reiterated his belief that Ole Gunnar Solskjaer will be sacked.
When asked if it should be up to Solskjaer to make sure United’s players are ready and motivated, Keane told Sky Sports: ‘Truthfully, no. I don’t think so.
‘The manager’s job, of course he’s got to oversee everything, but I never looked at a manager all my career before a match, and I’m talking about great managers and some bad managers going back to when I was eight years of age, I never looked at a manager to say, ‘are you going to motivate me today?’, that comes from within, that comes from your DNA, what you stand for, your background, your background, your family, your teammates.
‘The guys turned up today, we looked at the warm-ups, I’m intrigued when I look at the warm-ups, Cavani never tried a leg, he didn’t actually do a warm-up did he.
‘And then he’s coming on as sub for Manchester United going, ‘can you get us back in the game?’.
‘Ole will pay the ultimate price, obviously. Ole will lose his job working with this group of players, as night follows day, that’s what’s going to happen.
‘I’ve been saying it for the last month or two, but you still think, ‘you never know in this game. Things might change’, and you think it’s up to Ole to motivate these players to turn up against Arsenal at home?’