United are into the Europa League semi-finals after Marcus Rashford sealed victory over Anderlecht in extra-time of a match which saw both Marcos Rojo and top scorer Ibrahimovic forced off with injuries.
Jose Mourinho manager of Manchester United applauds the Anderlecht fans after the UEFA Europa League quarter final second leg match between Manchester United and RSC Anderlecht at Old Trafford on April 20, 2017 in Manchester, United Kingdom.
Mourinho said of the injured pair: 'I want to wait, but my feeling is not good for both.
"I want to wait and I want to try to be optimistic, but I'm not".
But Ibrahimovic's departure actually added impetus to the United attack, allowing the introduction of Anthony Martial, who replaced Marcus Rashford out wide on the left while the young England striker moved into a more central position up front.
Henrikh Mkhitaryan gave Manchester United an early lead with an excellent finish in the 10th minute of the first half.
On this occasion, at least, United rescued themselves with Rashford's goal but Mourinho will know his side must discover the killer touch from somewhere if they are to secure the Champions League place that must be the minimum requirement for this season.
After Paul Pogba played a wonderful through ball to Marcus Rashford down the left channel, the England forward, initially, tried to find Zlatan Ibrahimovic.
However, Anderlecht got themselves back on level terms just after the half-hour mark, with Sofiane Hanni netting from close-range.
Jose Mourinho remains on track to win two major trophies in his first season at Manchester United. "You have to try to do everything to accelerate the process". "We have great examples of fighters, of people with the right mentality". "I imagine the players are more exhausted than me but we are in the draw [on Friday] and we still have the dream to win the competition".
Despite this scoreless streak, Mourinho stated that he never lost confidence in the prodigious teenager, unlike other United players who "don't realise what makes me (Mourinho) trust a player".
Celta Vigo, Ajax and Lyon joined United in the semi-finals on Thursday.