Even though the situation is very difficult, Manchester United still has a chance to qualify for the round of 16. The only way for Manchester United to qualify for the last 16 is to win against Bayer Munchen and hope that the match between Copenhagen vs Galatasaray ends in a draw. Even though it's tough, in football anything can happen.
I agree with you. Although the situation is getting difficult for Man United but the chance isn't over yet. Winning against Bayern Munich isn't impossible if Bayern Munich won't play with their main players and with serious efforts. Bayern Munich possibly use their second tier players because they already qualified for the next round. I think Bayern Munich will prefer to let their main players to take a rest. Meanwhile for the match Copenhagen vs Galatasaray, it is difficult to predict the result of the match. But it is surely not impossible to end with a draw. If both teams play all out, a draw can be the reasonable result.
Bayern Munich will likely form their second tier squad. Even so, Manchester United's chances of winning are slim, even with Bayern Munich's second-tier squad. Their defense is quite weak. On the other hand, Bayern Munich plays attacking strategy. Manchester United's defense is unlikely to improve in front of Bayern Munich's attack. I don't think United will win this match. But since the match is not important for Bayern Munich. So the match is likely to be a draw. Bayern Munich drew goalless against Copenhagen.