The club's treble-winning skipper was highly critical of the veteran centre-back and England winger during his old side's scrappy win over Shakhtar Donetsk at Old Trafford
After consecutive home defeats in the Premier League, the Red Devils scraped past Shakhtar Donetsk on Tuesday in the Champions League thanks to a 62nd-minute Phil Jones goal - a victory which sealed top spot in A.
It was a far from convincing display, however, and Keane singled out veteran centre-back Ferdinand and the out-of-sorts Ashley Young as high-profile players guilty of letting down their under-fire boss.
"There has been no reaction from the United players from the disappointment of last week. They don't look like a team, just a collection of individuals running around," the former midfielder said on ITV during the half-time break at Old Trafford.
"You can defend players for making mistakes but you cannot defend players for not tackling and not getting close to people.
"[United] had a couple of good chances through Ashley Young towards the end of the first half. He should certainly hit the target. I think it sums up his time at Man United: just not good enough.
"David Moyes took the heat off the players before the game by saying it is his responsibility but we are talking about experienced players.
"Rio Ferdinand's decision-making, the chances he has taken, it is ridiculous. It [was] like his debut.
"As we said before the game, there are big question marks over the manager and the players. That, for Manchester United, is certainly not good enough."
The 42-year-old Keane seven Premier League titles and one Champions League during his United career, while he was also named PFA Player of the Year in 2000.