The German side currently sit third in the Bundesliga and progressed to the competition's round of 32 after finishing second in Group K.
Leverkusen secured five clean sheets from their six group matches and will need to show similar defensive resolve when Benfica arrive at the BayArena on Thursday - something right-back Carvajal is all too aware of.
"Benfica have a lot of quick players up front," he told the club's official website. "We'll have to be on our toes in defence.
"On the other hand, if we're on top of our game then we'll be really hard to beat.
"They're a very, very good team and they will make life really difficult for us.
"I think the strikers Oscar Cardozo and Rodrigo and the defender Ezequiel Garay are among their best players.
"The fact they managed to earn a draw against Barcelona at the Nou Camp in the Champions League group stage demonstrates the outstanding quality of the team."
One of the players mentioned, Rodrigo, happens to be a good friend of Carvajal's.
"I played alongside him for six months at Real Madrid and we're regularly in the Spain Under-21 squad," he said.
"He's a great bloke and I'm looking forward to meeting him again."
The Spaniard is hoping for a clean sheet in Thursday's match ahead of the return leg at the Estadio da Luz.
"I've never played there but I've heard it's a great stadium with fans who really get behind their team," Carvajal added.
"It will be important to get a result in the home game to give us a cushion when we go to their place.
"It would be good to keep a clean sheet and score one or two at the other end."
Thursday will be Benfica's first Europa League game of the season, having finished third in Champions League Group G.
Most recently they battled through to the semi-final in 2011, bowing out to fellow Portuguese side Braga.