The former England global won five Premier League titles, the UEFA Champions League and Europa League, the FA Cup and the EFL Cup on three occasions during his time at Old Trafford.
Herrera added: "Yes, City is in a very good place and only a miracle will give us a chance - but you don't stop". "But when a team arrives in the last eight, anything can happen".
However, I can see him having another frustrating evening, knowing he's not got the supply or support to show his potential, and will be left day dreaming of playing against Barca for Real Madrid next season. "Sometimes you are in the team, sometimes you are not in the team".
Getting to the quarter-finals will be special for the club which has only played once in the quarter-finals during the past 60 years.
It's been one of the best spells in Manchester United's season in recent weeks.
Sevilla drew 2-2 at Liverpool in the group stage and came back from 3-0 down at home to draw 3-3 with Jurgen Klopp's side, with Mourinho acutely aware of their goal threat.
"Not looking past Tuesday night, but for seasons ahead now I think as a squad we need to develop, we need to be constantly in this position and expect it of ourselves and keep them standards high". It's a team with a big tradition.
"This isn't a vintage United side, but it's not as bad as the detractors would suggest", Andy Mitten, editor of the United We Stand fanzine, said. "But we will try". "So not to win would be a disappointment". Now, attention turns to further progression in Europe and the Reds will be confident of maintaining our strong home form, having won all five games at Old Trafford in all competitions so far in 2018.
Mourinho's men are now locked at 0-0 in a two-legged European tie and Herrera is determined to help the Red Devils reach the last eight of that competition.
Saturday's win over Jurgen Klopp's men came after a superb double from Marcus Rashford and it consolidated United's grip on second place in the Premier League table.
Manchester United host Sevilla on Tuesday in a match that will see the victor going through to the quarterfinals of the Champions League.
Charlie Nicholas is back with with his European predictions as Manchester United and Chelsea look to progress in the Champions League, while Arsenal have a healthy lead to defend against AC Milan in the Europa League.