Victor Wanyama and Harry Kane secured Tottenham victory in the final game at White Hart Lane, with Wayne Rooney pulling one back for much-changed United as they slipped to a 2-1 defeat.
"We know what we are doing and if we can win a third trophy [after the Community Shield and the EFL Cup] it would be magnificent for us because we know that it's a big objective".
"But if you look at the history of this club when they've been successful, they had three or four top strikers who have rotated".
Mourinho has been a constant critic of the fixture schedule this season, with runs in the FA Cup and Europa League adding to 38 Premier League games.
Explaining his decision, Mourinho insisted he will continue to make major changes for each of the club's last three league matches up until the final against Ajax in 10 days.
The former Reds midfielder admits the Portuguese's move paid off, but he is desperate for Ajax to keep Manchester United out of the Champions League next season by winning the Europa League.
"I analyse the individual performances of the players", Mourinho said. Moreover, United were besieged with injury troubles and Mourinho made it clear that it was impossible to fight on two fronts with just 15 players. I can not lose 5-0 or 6-0.
Following today's 2-1 defeat, Mourinho spoke to Sky Sports about his frustrations at the injury crisis.
Man Utd goalkeeper David De Gea could reportedly be denied the opportunity to play in the last Premier League game of the season at Old Trafford.
"After 2-0 we had to bring a bit more quality to the team, we brought more balance", Mourinho said in his post-match press conference.
'The two goals are bad to concede but the team is not used to playing together'.
"We didn't gamble - what we did was compulsory". At the moment, the Premier League matches are the ones we do not want to play. The ones that needed to play played 90 minutes and I rested a few people.