Four-time defending champion Sebastian Vettel looks set to finally concede in the drivers' race, sitting 117 points behind Mercedes' Lewis Hamilton with five races remaining.
The German has also failed to win a race on the F1 circuit in 2014, while team-mate Daniel Ricciardo has done so thrice.
Ricciardo is third in the standings behind Hamilton and Mercedes team-mate Nico Rosberg, 60 points off the leading Briton and Red Bull's best hope of pinching the silverware.
But despite the pair's significant handicap, Horner said he was not giving up on a comeback - with double points on offer in the season finale in Abu Dhabi in November.
Horner also claimed Mercedes' poor reliability - which led to Rosberg's race retirement in Singapore - could be a factor in helping his garage reel in the runaway leaders.
"Due to their [Mercedes'] shocking reliability, hopefully we can keep ourselves in the championship," he said.
He added: "Mercedes have an enormous advantage at this point.
"We'll take it one race at a time. Both of them are still just in it and both have taken a chunk of points out of Nico.
"Daniel, OK he's conceded three points to Seb [in Singapore] but is that going to make the difference? Impossible to say with a crystal ball at this stage but at the moment it doesn't make sense to interfere with team orders.
"Daniel is totally comfortable and happy with that.
"If there was a realistic chance of Daniel winning and Sebastian was mathematically out of the championship, then we'd do the best we can for the team but the situation we're in at the moment is it's a long shot."
F1 returns to action at the Japanese Grand Prix on October 5.