"You need to remember that Dutch players coming to England with great quality have always needed time," said the Reds boss.
"Robin van Persie was like that and Dennis Bergkamp also needed time. The leagues are totally different.
"The Dutch league is very technical and you have two or three teams that are very good.
"Every game is about getting the ball, keeping the ball and playing nice football.
"Here it is harder, though Babel has played some fantastic games for us.
"So we still have a lot of confidence he can progress, but now he has to work hard on defence and learn how to challenge players.
"He has done well as an impact player, which is not easy when you are young, but we think he can do more than that for us.
"Our view of Ryan is a player who starts games and has an impact from the beginning, not just as a sub.
"But first of all he has to improve tactically and we are working with him on that.
"He is the kind of player who can change games and he has done that when coming from the bench.
"Now we want him to start games and change them."