Man, Souichirou completely stole this episode. Despite being a dull, boring old man, he knows how to pack a punch. Poor Saber is on the receiving end of everything. I swear she’s always getting the short end of the stick when it comes to the Fate series. She’s always hyped up as the strongest class (or one of) but she never really overwhelms her opponents.
Jikman's Anime Zone 
Mostly to do with the amount of mana she is receiving. Shirou by any means is an inept magi, who can not produce enough mana to allow Saber to fight at full strength. Keep watching this show though.