Levi looked towards Kotomine and nodded. "I am familiar with the rules yes, no questions." And then he looked towards Archer.
"I know we were vulnerable and it was less of a stamina related issue than something more akin to forced mediation. But regardless if we had remained in our fortified base of operations as I had suggested then no risk would come to you or I. But your impatience and the realisation that unless I state it as a direct order you will be rebellious is worrying. To win this war, you must trust I know what I am doing." 

Levi turned to leave the church. "I placed my blood, sweat and tears into summoning you specifically, literally and figuratively. Will you trust me Archer?" Levi said as he moved towards the door. "Because more that I need to trust you, I want to trust you." And then he continued walking. 

His servant thought him weak, was he aware of the complexity of his summon, that linked him to the Ouroboros, something strong enough to sustain his mana. Levi wasn't sure, but regardless this was not for him, if was for Archer and for his brother.