The Argentina striker is doubtful for the encounter at the Liberty Stadium after hurting his back in Sunday's 2-0 triumph at Sassuolo.
"Higuain sustained a knock on his back and we will have to evaluate his condition," Benitez said to www.sscnapoli.it.
"It's early to evaluate whether he (will) play on Thursday or not."
Higuain is Napoli's top scorer this season with 18 goals in all competitions.
Napoli go into their midweek encounter in Wales on the back three straight wins in all competitions.
Moreover, the Naples outfit have scored eight goals and given away just one in that stretch.
The Azzurri, who qualified for the Coppa Italia final last week after eliminating Roma in the semi-final stages, are third in Serie A and hold the last Champions League qualifying spot.
"We must now turn our attention to Thursday's game against Swansea," Benitez said. "It's going to be a difficult match because we will be made to work by Swansea in order to keep possession."
Napoli host Swansea in the return leg on February 27.