Barcelona coach Xavi says facing Manchester United is a "difficult test".
Barca host United this week in the first-leg of their Europa League playoff.
After victory at Villarreal, Xavi said, "I will not say that [Barcelona are unstoppable], but we're in a good moment, a perfect moment in defence.
"In the intensity, the high pressure, we recovered one ball today that we could have scored the 1-0.
"That's very important to us, the intensity and the rhythm. Of course, it was really tough to dominate the game, because they pressed high for the 90 minutes, so it was difficult and we needed to win the duels today.
"If we win the duels, it's an attack for Barcelona. I'm very happy and satisfied. Now we need to recover well, change the mentality for the Europa League and show our best level against Manchester United, as they're also in a really good moment.
"It's a very difficult draw, they [United] are a very difficult team, but okay, let's compete. We're in the best moment since I came here as a coach."
