With a stalemate looming and the visiting fans' ire for Benitez and Torres increasing, Oscar came off the bench to score the winner eight minutes from time to give last season's Champions League winners the advantage ahead of next week's second leg of the last-32 tie at Stamford Bridge.
"Eighteen attempts away is not bad, but we have to be more clinical in attack," Benitez said.
"The first 20 minutes we were in control. We had some half chances; it was a cross, we weren't there. We were in control.
"After this 20 minutes they were pushing and pushing. The team, as a team, had problems defending.
"We changed a little bit in the second half. I think the concentration of the team was much better, the intensity in defence was much better and then we had more control."
Many of the missed opportunities fell to Torres, who now has one goal in 13 games.
Benitez, who managed Torres at Liverpool, refused to criticise his compatriot, even though the World Cup winner did not make an effort to meet two early crosses from Eden Hazard and looked disinterested at times.
"We have to create more opportunities and the strikers will score more goals," Benitez said.
"His work rate was really good and thanks to him the rest of the team, especially the second line of offensive players, they could create."