It was stated that Kojiro and Berserker fought every Servant, but we only saw

>Saber vs Kojiro (Fate route)
>Archer vs Kojiro
>Saber vs Kojiro (UBW route)

>Saber vs Berserker (Fate/HF route)
>Saber & Archer vs Berserker (UBW route)
>Archer vs Berserker (Fate route)
>Gilgamesh vs Berserker (UBW route)
>Dark Saber vs Berserker (HF route)