Winning the tournament earns them a spot in next season's Champions League, so it's just as good as a top four Premier League finish.
Mourinho will certainly have approved of the final result at the Stadium of Light, which sees United move to within four points of the Champions League places.
"Most of the players in Manchester United are young - we are here to learn", the 22-year-old defender said.
"I thought about a half-time change but thought it was too harsh for [Shaw]", Mourinho added.
"He is playing amazingly well but even in the period he was not scoring goals he was important for us". "It was good to protect him".
Benjamin Button, a fictional character created by celebrated American writer F Scott Fitzgerald, was born with the physical characteristics of an elderly man and died as an infant boy.
'We don't hide that we are still fighting for our situation in the Premier League but the Europa League becomes a fundamental competition for us, ' he said.
"It's good for him to have a rest", Mourinho said.
Mourinho told BBC: "We want to fight in the Premier League until it is mathematically impossible. But we started the game, scored a goal and killed it".
Sunderland are likely to appeal the red card shown to midfielder Seb Larsson, but manager David Moyes was keen not to use the loss of the Sweden worldwide before half-time as an excuse for a fifth defeat in six games which pushed his side closer to relegation to the Championship.
The 26-year-old made several errors and had little command of his box, with it clear that he was struggling with the physicality of English football in his early years (he was even dropped in favour of Anders Lindegaard, who is now playing at Preston).
'I believe in what I do, I believe in myself and I know what I am able to do and I'm not anxious I just play my game and try to enjoy. Things today didn't go for us.
United needed goalkeeper Sergio Romero to spread himself at close range to deny Victor Anichebe Sunderland's first league goal since 4 February, and the hosts suffered another blow when Larsson was dismissed.