Ray Houghton thinks Scotland would have been in the Euro 2016 play-offs instead of Republic of Ireland had Gordon Strachan's side not lost to Georgia.
The former Ireland midfielder says that 1-0 reverse in Tbilisi did more damage to the Scots than the four points his side took from world champions Germany.
"I was in Portugal when we were about to play Gibraltar and Scotland were over playing against Georgia," he said.
"They lost and everyone got a huge lift from Ireland's point of view."
While Scotland eventually finished fourth behind the Irish to miss out on a play-off place to reach next year's finals, Martin O'Neill's side stand on the brink of qualification after Friday's 1-1 first-leg draw away to Bosnia and Herzegovina.
"They've had one bad performance and, for me, it was when they went to Georgia," said Glasgow-born Houghton.
"I just couldn't see them losing that game. Georgia haven't won too many.
"No-one anticipated it. Everyone thought Scotland were going to win, they didn't and I think that really affected them."
Scotland were held to a draw at home to eventual group runners-up Poland in their next match as the Irish beat leaders Germany in Dublin.
"That game against Poland - 2-1 up with a minute to go at Hampden, to throw away the goal like they did, I don't think the boys realised they still had a chance to qualify," said Houghton.
"If they had won that night and Ireland beat Poland then Scotland would have reached the play-offs and Ireland would have qualified automatically."
Houghton thinks there is not too much between the Irish and Scottish teams.
"In the two games we had against Scotland, both up in Glasgow and in Ireland, Scotland did well," he said.
"They maybe just about deserved to win the first game. Didn't particularly play well in the first half in Ireland but were much better in the second.
"I thought at that stage they were favourites to come in the top three, but I couldn't quite believe what happened."
Houghton thinks Ireland's knack of not conceding goals was what set them apart and is what could ensure their qualification after Tuesday's second leg.
"If you look at the form shown by Bosnia, in the previous six games since the new coach came in, they had won five and only lost the one to Belgium and there is no great shame in that," he said.
"Bosnia were favourites and to come away with a 1-1 draw was a great result.
"The emphasis is on Bosnia. They have got to score and have to come out at some stage and that's when you can maybe capitalise on their defensive frailties, because that's where they are weak.
"They are going to improve. They are not going to play as badly as they did on Friday night, but if we can defend well against them, Ireland have got some players who can cause problems as well.
"The boys have just got to hold their nerve."