The Brazil international apologised to the 19-year-old, who was left concussed when Luiz hit the youngster's jaw with his shoulder in the final few minutes of Chelsea's 4-0 win over the League One side in the FA Cup last week.
"I see hundreds of tackles in the league that are more dangerous than that one," The Express quotes Benitez as saying. "I won't say it wasn't bad, it wasn't the best, but a factor was the size of the other player. David Luiz is a great player and we have to be pleased he's playing in the Premier League. It was bad luck."