The French goalkeeper copped a stray leg to the head in the second half which almost forced a change in personnel as Brad Friedel prepared to step in.
However, Lloris was eager to keep playing which prompted Villas-Boas to retain his number one for the remainder of the Goodison Park stalemate.
"The medical department was giving me signs that the player couldn't carry on, because he couldn't remember where he was," Villas-Boas told Sky Sports.
"That is the situation right now - he doesn't remember the impact.
"But he was quite focused and determined to continue, so when you see this kind of assertiveness it means he is able to carry on, and that is why it was my call to delay the substitution.
"You have to make a decision in situations like this but from my knowledge of Hugo he seemed okay to continue.
"It was a dreadful situation. You can imagine the impact of a knee going against a goalkeeper's head.
"It happened unfortunately to Petr (Cech) so it is good that the players immediately went to him and it is very fortunate that it was nothing serious."
For the big stories and the banter follow us on Twitter: @tribalfootball