United beat Russian side Rostov 1-0 on Thursday to reach the last-eight of the Europa League and are sixth in the Premier League with 12 games to play.
And Mourinho has called for the Premier League to help protect English clubs as they challenge in Europe's top cup competitions.
"Convincing this was most certainly not, the night following a similar theme to many games at Old Trafford this season, with United carving enough chances to put the game to bed early on only for that familiar wastefulness to leave them vulnerable after the interval".
The last time Boro were relegated was 2009 and it took the club seven years to make it back.
Man United came second in their group stage after winning four and losing two of their group matches before defeating French club Saint-Etienne in the last 32 with Ibrahimovic scoring a hat-trick in the first leg of the tie.
Middlesbrough's caretaker boss Steve Agnew: "I have to be honest, [Thursday] was a really hard and emotional day".
Agnew will be hoping to have Calum Chambers, Daniel Ayala, George Friend, Rudy Gestede and Bernardo all available after recent knocks, although Gestede has seen his dismal record at Premier League level extend to only one win in 41 games for three different clubs.
Manchester United manager Jose Mourinho has launched a scathing attack on Premier League officials, claiming they "simply don't care" about teams who are competing in Europe. "I think we are".
Second-bottom Middlesbrough are without a manager after sacking Aitor Karanka and Mourinho gave a sarcastic response when he was asked about the fate that has befallen his former Real Madrid assistant. "I'm sick to death of him".
United head coach Jose Mourinho expected Pogba to be sidelined around three weeks, forcing him to withdraw from the clash with Middlesbrough in the EPL, in addition to his French national duties.
"Obviously it was a disappointment on Monday that we went out - it could have been another trophy in a season where we have already won two", Mata said. "Even a physical monster like him felt it".
"Man. Utd. sold players that I would never sell, bought players that I would never buy".
"Because of the nature of the club and of myself, we are ready to fight for every game, every point".
"So that's normal. I think the Monday game, more than an hour of 11 against 10, also had a price".