In a casual email, I just wrote:
Mais avant tout, si j’en suis là où je suis aujourd’hui, c’est justement parce que je suis très bien entouré ; mes collaborateurs, qui en connaissent un rayon, y sont sans doute pour beaucoup.
By the expression "en connaître un rayon", I wanted to say that my co-workers shine in everything French language, knowing grammar etc inside out. They basically know what they are doing, know their stuff.
If it is obvious from context what field/subject they excel in, is it common to omit "en matière de ...", "sur ...", or "là-dessus" after "rayon"? Does adding those extra words come across as redundant?
If you use other expressions such as "être calé en qch" or "s'y connaître en qch", you do include the idea of "what field/subject", so I'm all the more curious about how it works with "en connaître un rayon".