Pep needs to watch out for Valverde if he wants to do something against a 3-0 deficit. It's not just Valverde; every Real Madrid player is excellent on a good day, making them very difficult to defend against. Guardiola was at least lucky that Vinicius Jr. missed his penalty. If he hadn't missed and scored, it would have been 4-0. Manchester City must use all their chances in the return leg and showcase all their abilities. It's not impossible, there have been comebacks like this before, but it's closer to impossible.
I don't think Valverde is the only player Pep needs to be wary of, as Real Madrid's midfielders and wingers also need to be watched closely.
If Pep wants to have the potential to win in the second leg, he must ensure his players can effectively limit Real Madrid's midfield and wingers.
This will certainly hinder Real Madrid's attacking flow. However,, this won't be easy for Manchester City players, as Real Madrid will likely be more confident in their performance in the second leg, which will certainly make things difficult for Manchester City. Therefore, I think Pep must ensure his players don't concede a single goal and must be able to score more than 3 goals to win. But honestly, this is very difficult to make happen, but yes, Manchester City must not give up, because basically, as long as the ball is round,, anything can still happen.