The Spaniard had hoped to push Manchester City for second place but the Blues now find themselves looking over their shoulders after they were beaten 2-0 by Roberto Mancini's team on Sunday.
Tottenham could leapfrog Chelsea into third by beating West Ham on Monday night and Arsenal trail Benitez's team by only two points.
|1/5||Chelsea are 1/5 with Bet365 to finish in the Premier League top four
Goals from Yaya Toure and Carlos Tevez sealed Chelsea's defeat after Joe Hart saved a Frank Lampard penalty, denying the midfielder his 200th goal for the Stamford Bridge club.
Benitez admitted that the 50th-minute spot kick was a turning point despite his team's unspectacular performance until that point.
"The penalty is a crucial moment; we did not do as well as we were expecting but the penalty could have changed everything," he reflected.
It was a good penalty and a good save. 10 minutes later, they score. Then we have to take a risk and it is clear they are a good team."