Brennan Johnson’s 42nd-minute close-range finish helped Spurs beat United 1-0 to win the club their first trophy since 2008.
Tottenham’s celebrations were contrasted by images of crestfallen United players who are now left with nothing from a disastrous season, with Keane giving his verdict on their performance to CBS Sport.
“Just when you think things can't get any worse for Man United. It's been the story all year,” said Keane.
“They've been getting out of jail with European football and it's been covering the huge cracks at Man United.
Manchester United's Bruno Fernandes (centre) and team-mates appear dejected following defeat in the UEFA Europa League final at the Estadio de San Mames in Bilbao: Nick Potts/PA Wire.
Manchester United's Bruno Fernandes (centre) and team-mates appear dejected following defeat in the UEFA Europa League final at the Estadio de San Mames in Bilbao: Nick Potts/PA Wire.
'I don't think that there will be a better person to come into the job' - Bruno Fernandes on Ruben Amorim
“All season they have been so easy to beat, so this is no surprise. They got lucky a few times in Europe and then tonight again, ultimately it's not good enough. They didn't show enough quality. Not enough options off the bench.
“If you're depending on Harry Maguire [as an emergency striker] to get you out of jail at the end of the game, it sums up their problem.
“United have a real lack of quality, but it was a great night for Spurs. We worried at the start of the second half that they shut up shop early at the start of the second half, but they defended so well. Well done to Spurs.”
Keane was critical of United’s defending on Johnson’s winning goal, with Luke Shaw failing to deal with the ball into the box before Johnson got the decisive touch.
Manchester United's Bruno Fernandes (centre) and team-mates appear dejected following defeat in the UEFA Europa League final at the Estadio de San Mames in Bilbao: Nick Potts/PA Wire.
Manchester United's Bruno Fernandes (centre) and team-mates appear dejected following defeat in the UEFA Europa League final at the Estadio de San Mames in Bilbao: Nick Potts/PA Wire.
'I can say 100pc now, he's the right man' - Luke Shaw on Ruben Amorim
“I think the goal summed up the game. There was a real lack of quality,” stated Keane.
“Spurs aren’t doing anything extraordinary, it’s all pretty simple play. That’s where you have to be really critical of United’s defensive shape and decision-making.
“We discussed before the game, when it does go wide and the ball’s put in… players not doing their jobs, not concentrating. Shaw is maybe not match fit, Maguire is focused on his man. Remember there’s only one ball. Just focus on the ball sometimes.
“We ask our defenders, people talk about midfielders doing their job… you’ve got to multitask.
“It’s as if like, “I’ve got my man here!”, but no, you’ve got to multitask and do more than one job.
“It’s far too easy. It’s been like that all season for United, far too easy.”
Roy Keane
Roy Keane
Keane also suggested Spurs boss Ange Postecoglou may now stay in his role for next season, even though he has overseen a hugely disappointing Premier League campaign.
“Whether the club made a decision before this I don’t know because the league form has been so bad, we can’t forget that,” he added.
“Obviously, they can enjoy tonight. But when you reflect on the season, it hasn’t been good enough.
“But it’s a nice problem now for the club to have. They are in the Champions League. You would like to think the club would want him to stay on and give him a chance to impress again next year. A big transfer window is coming up.
“They will have financial backing, of course, because of the reward that comes with winning tonight. I hope he stays on – he has been there two seasons. A very good first season. The second one was difficult. Give the man a chance. Why not?!”