Speaking to Sky Sports, he said: "I think the top teams have always performed well, but I think the mid-table clubs are getting better and better and it's becoming very physical with the amount of games.
"There are no easy matches and you have to give 100% every week. That's maybe a bigger challenge to how it was a few years back.
"As we know, the Premier League is the most competitive league in the world and that's why not every player can cope with the league."
The Spain international added: "As I've been saying, they're a very physical side who mark man-to-man across the whole pitch.
"They are very strong and I said, we have to match the intensity and then hopefully with quality we have, we can hope out on top."