Ally McCoist believes Rangers can retain their Scottish Premier League crown even if reinforcements are not signed in the January transfer window.
His side were knocked off top spot by Celtic thanks to Joe Ledley's second-half close-range header.
"If we get fresh blood in January that would be great, but if we don't I certainly believe we can go on and win the title," said the Ibrox manager.
"But it will be very difficult, as it is to win any championship."
McCoist added: "As manager of this football club, I have to believe [we can win the league] and I do believe."
On 5 November, Motherwell were Rangers' closest challengers, with Celtic, having played two games fewer, 15 points behind their old rivals.
But Rangers have let slip 11 points from a possible 21 in the SPL since their goalless draw against St Johnstone on 19 November, while Neil Lennon's Celtic have racked up nine consecutive victories.
"If you look at the game, we are disappointed but you have to look at the performances and the way the boys went about their work today," said McCoist after Wednesday's defeat at Celtic Park.
"There is plenty of effort and commitment and attitude to play. There is a real desire to work for each other to get the result.
"I don't have any problem with picking the boys up because they will be fine.
"We are halfway through the season so there is a lot of football to be played."
Rangers had two attempts on target to Celtic's nine, though they might have been awarded a goal when Lee Wallace's header was palmed away superbly by home keeper Fraser Forster.
Television replays were inconclusive as to whether the whole ball had crossed the line, highlighting the difficulty facing referee Willie Collum and his linesman in making an instant decision.
McCoist felt his 4-4-2 set-up was positive and justified but did acknowledge his team is "maybe not firing on all cylinders up front".
"I wanted to have a go. I wanted to come and be a presence and attempt to pose Celtic problems," reflected McCoist.
"We played with the two lads up front [Nikica Jelavic and Kyle Lafferty] and Sone [Aluko], who started the game well but we probably couldn't get the ball to him enough.
"My overriding thought is one of disappointment.
"I didn't think there was an awful lot in the game. Defences were reasonably comfortable and reasonably solid without giving up too many chances.
"I said to the boys at half-time, 'you cannot afford to drop any level of concentration'. I think we did that and that is what cost us the game.
"I think we started the second half all right but we switched off and found ourselves a goal behind."