The Bosnian goalkeeper left Stamford Bridge in the summer to join Bournemouth after collecting a title medal with the Blues last season.
He told the Daily Echo: “It is a long season and there are still almost 30 games left.
“Manchester City are flying at the moment but so many things can happen.
“You can have injuries, suspensions and a loss of form. I wouldn’t rule out Chelsea just yet.”
Begovic will come up against his former side for the first time on Saturday when Chelsea travel to the Vitality Stadium.
The 30-year-old added: “They are a great team and we know we are in for a huge test against them.
“It is a game we are looking forward to, especially following the Stoke win. We needed that and it will give us confidence.
“We will go into the Chelsea game with nothing to lose and give it our best.”