United are gearing up for their first Champions League match in 644 days when they host Basel at Old Trafford on Tuesday, having qualified for European football's premier club competition by winning the Europa League last season.
Herrera believes that the Red Devils are back where they belong, but warned against expecting too much from the three-time European champions upon their return to the biggest stage.
"We are ready but we have to respect every opponent and realise where we have come from. We are a big club and maybe the biggest in the world, but we were not in the Champions League last season and we have to take it step by step. First aim we have is Basel. We cannot think of winning the Champions League now, we have to take it one step at a time," he told reporters.
"We should be in the Champions League. Even without the Champions League we are the club with more fans than anybody in the world, with the biggest amount of sponsors in the world, but being in the Champions League is basic for us, that is why the game against Ajax was the game of our lives. It was certainly the game of my career.
"We want to fight for every title. Last season we won three which wasn't bad for the club, but we did not fight for the Premier League and we were not in the Champions League, so we have to be humble and take it step by step. It is amazing to be back in it. Every game is amazing for Manchester United for me but the Champions League is the most beautiful competition apart from the Premier League."
United have also been drawn in a Champions League group with Benfica and CSKA Moscow.