A fielder's height will give him problem anywhere in the field, not just slip.
Can't agree with T_E here though... slip is infact a specialised position. Or else any good fielder of any team would be placed there, without feeling the necessity of someone 'special' to do the job. Like you have your preferred gully/point fielder, you also have your preferred slip fielder. Players like Graeme Hick, Mark Taylor are specially known for their expertise at the clip cordon.
Just look at it like a batting order of a team. There are special batsmen for special positions in the order. Or else, any good batsman would bat anywhere in the order.
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