Rovers confounded their critics by finishing 12 points above the relegation zone in May following a dreadful start to the campaign, but the sale of Player of the Year Matt Mills and Richie Wellens during the summer has left a gaping hole, according to the Rovers manager.
O'Driscoll told the club's official website: "We're not as strong as last year after losing two players, so we're in a bit of a difficult position because the job of trying to improve the team takes a lot more resources than what we've got.
"We've got to do it in a different way. We're trying to hit the same players with different problems and different challenges."
O'Driscoll added: "We're in a different phase. Ideally, if we had kept what we had got and added one or two, then I think we would have moved on a little bit, but losing two players is inevitable for a club of our size.
"We're probably a little bit behind where we want to be, but that's no fault of anybody's, that's the industry we're in."