The La Liga leaders will face Liverpool in the last four if they can beat Porto this evening.
The Reds are 2-0 up after the first leg at Anfield.
Messi was blunt in his criticism of Barcelona and their slow star against United.
“We cannot start like this in any Champions League game,” Messi told reporters.
Lionel Messi praised after performance against United
Lionel Messi could face Liverpool star Mohamed Salah in the semi-finals (Image: GETTY)
“We said that from the start, we had the experience of Roma, you can’t afford to make life hard for yourself because one mistake can knock you out of this competition.
“We have to be aware of that.
“We have become much more solid, over the season we struggled a little bit at the back but the whole team is making a huge effort and that makes it far harder for opponents to attack us.
“We had been three years without making the semi-finals but we didn’t have any negative feelings.
Invalid email
We use your sign-up to provide content in ways you've consented to and to improve our understanding of you. This may include adverts from us and 3rd parties based on our understanding. You can unsubscribe at any time. Read our Privacy Policy
Lionel Messi is the top scorer in the Champions League this season with 10 goals (Image: GETTY)