In the continued absence of Fabio Aurelio, centre-half Daniel Agger has played the last two games at left-back.
Aurelio could soon be back training with the first team and Benitez hopes to see Insua back before the final match at Hull next month.
"Emiliano is doing well but it's a bad injury so we have to wait. He's working and having treatment,'' Benitez said.
"He tore his quadriceps. He could play again this season if the treatment is good. It will be difficult but we'll see - we're trying very hard.
"Fabio is doing well too. Maybe in one week or 10 days he can be ready to train with the team. If Fabio can be ready it will be very important.''