The keeper and the seeker: the two most important jobs on a quidditch team.
If you think about it, you can win a quidditch match with only a keeper and a seeker. If they are very good.
The Gryffindor seeker is the good looking, famous one. He's the one everybody knows. He's the one everybody wants to know.
The Gryffindor keeper is different. He's the tall, gangly red head, with a face full of freckles. He's quite poor, and not the best. He's always in the shadow of someone.
But without both of them, the match will surely be lost.