Chelsea are known to be in the hunt for a new striker with Atletico Madrid ace Radamel Falcao high on the wanted list, but following the injury to Oriol Romeu a new midfielder is also required.
The only other recognised player in that holding position is John Obi Mikel and he will be on African Nations Cup duty next month. The Blues have been linked with the likes of Corinthians' Paulinho, Newcastle's Cheick Tiote and Everton's Marouane Fellaini and Benitez has hinted that players will be brought in.
"The club is working and always looking for good players, so we'll see if there are any surprises," he revealed.
Benitez admitted the seriousness of Romeu's injury, which he suffered in Saturday's Barclays Premier League win at Sunderland, had taken Chelsea by surprise.
"Oriol Romeu was bad news and we weren't expecting something so serious," he added. "He'll be fine for the future, he's a young player."