"Some players like Pires and Henry took four, five, six months and they became exceptional players," he told Arsenal Player. "Park arrived two months ago so that's normal.
"Some people judged our players very quickly in a negative way and slowly they changed their mind through their performances. I prefer it that way round than the other. Some players make you jump off your seat in the early stages and then disappoint you after. These players will win over all the sceptical people and Park is one of them.
"I have been impressed by his intelligence and his attitude. He is well-appreciated and rated by his team-mates and by the staff as well - we think he is a quality player.
"It is hard in the Premier League but Park is a player with quality and intelligence. On the longer term that will always come out and I am confident he will do that in the Premier League as well.
"What you need when you want to be successful at a club is three strikers, three central strikers. We have them and we are very happy with that."