Swiss player Roger Federer on Tuesday highlighted the importance of maintaining integrity within tennis, a few days after Spain's Fernando Verdasco caused a controversy after shouting at a ball boy.In a video released a few days ago, Verdasco can be seen losing his temper with a ball boy for being too slow in bringing his towel during a semi-final match at the Shenzhen Open last week, reports Efe news."I still think we are doing actually very well in our sport, and we have to maintain that, you know, the integrity and the way we treat each other, because it is a classy sport, tennis," Federer said at a press conference here, where he is seeking to win his 3rd Shanghai Masters title."The ball kids are really important to us, because they are also maybe the future of our game, like I was," added the world no. 2.Verdasco's behaviour, for which he was handed a warning by the umpire, has prompted the Association of Tennis Professionals (ATP) to consider changing the rules to spare ball boys and girls from handing players a towel, instead installing hooks on court.Federer described the incident as an "exception" that sometimes happens "in the heat of the moment" and said the work of the ball kids in bringing players their towels helps save time."Well, I think the idea of having the ball kids bring it to you is to speed up the points, you know, in between. If now you've got a hook or a rail in the back, I don't know. It's like are you wasting extra three seconds of time each and every point?" he explained.Federer, who is defending his title in Shanghai, will play his second round match on Wednesday, against the winner of the match between Russia's Daniil Medvedev and China's Ze Zhang.