Weir was No 2 to Mark Warburton when the Englishman guided his team to a penalty shootout success over the Parkhead side at Hampden.
That came in the wake of Rangers having clinched the Championship to claim a place in the Scottish top flight five years on from liquidation. Everything then seemed to be pointing to Rangers returning to trophy-winning mode – as the club’s support craved.
Instead, the subsequent Scottish Cup final was lost to Hibs and, within ten months, Warburton and Weir had lost their jobs as Celtic lost any sense of vulnerability thanks to new manager Brendan Rodgers.
If Rangers do win Sunday’s semi-final rematch at Hampden, it would not lift them to equal status with their old rivals. Although it would end a nine-game derby winless run and burst Celtic’s double-treble hopes.
Weir said: “In hindsight, I think, definitely, beating Celtic probably heightened a lot of people’s expectations in terms of where Rangers were really at, at that time.
“But Celtic reacted to that too. They reacted very well. They went out and got a great manager.
“We were a Championship team with a lot of lads who were having their first experience of Rangers and were learning about the club and the expectations.
“The biggest thing with finally beating Celtic was that Rangers were on their way back. It was a watershed moment for a lot of people and there was an outpouring after that of ‘Rangers are back’.”
Even before Celtic were able disabuse the Rangers faithful of the notion that there was a serious threat to their dominance, Weir’s stint on the Ibrox management team had taken a dramatic turn for the worse through the failure to hold on to a 2-1 lead in the final nine minutes of the Scottish Cup final against Hibs to bring the curtain down on his first season at Warburton’s side.
Rangers subsequent inability to suggest they could finish a strong second to Celtic in the Premiership meant Weir and Warburton didn’t even see out a second season.
Their acrimonious departure was wrapped in claim and counter-claim between Warburton and Rangers chairman Dave King over the circumstances of the parting.
And Weir acknowledges that his time on the coaching staff, which followed a medal-laden six years as an Ibrox player, elicits a mixture of pride and frustration.
The 47-year-old said: “You want to go to Rangers and be there for a long time and be successful.
“I will argue with anyone that we were successful at Rangers. When we came to the club, we had nine players, the club had finished third in the Championship and there was a lot of work to be done.
“We wanted to build a team to take Rangers into the Premiership and a lot of work went into that.
“We were on the right route getting Rangers back to where we wanted to be. But the next season was more difficult back in the Premiership. There were obstacles in our way, some things did not work out the way we had hoped and we had to readjust as we were going.”
Weir is currently out of the game after an ill-fated nine-month stint as No 2 to Warburton at Nottingham Forest ended four months ago.
He added: “It does take time [to accept how it ended at Rangers] and probably still you’re not really sure how it happened and what happened. But that’s football, you can’t live your life full of regrets, you move on. That’s kind of how I see it.
“You’re not happy with the way it ended and you want to get your side of the story out, but what is the point of that? There’s no point in dragging it out, you’ve got to move on and you’ve got to get your priorities right and focus on the future.
“You can’t change the past, you can’t change what’s happened and the circumstances, so why worry about it or over-analyse it? You’ve just got to learn from it and try to put it into practice going forward as often as you can.”
Weir’s analysis of how Rangers prevailed over Celtic in 2016 and how they could do so again is refreshingly honest.
Although he does agree with the general belief they were impressive in their play that afternoon against a bedraggled Ronny Deila side containing superior individuals, he ultimately believes their triumph came down to one element: good fortune
“The game itself was really exciting. But, being honest, Celtic should have won it,” said Weir.
“They had the better chances. Things went our way, even the penalties. [Tom] Rogic slipped at his penalty. It just seemed it was going to be our day.
“We were in a good position because we were winning regularly and the group was confident. The team was settled, everyone knew their role and how we were going to play.
“We were really confident even though Celtic were the better team with better players. There’s no doubt about that. But we felt we had nothing to lose. We were not expected to win but we felt we had a chance.
“Not unlike when we won that game, I think Rangers need a little bit of luck in terms of incidents in the game going their way. They will need to perform well, undoubtedly, they will need to take their chances when they come.
“On the occasion, we won we played really well, as well as we could have done on the day, and even playing as well as we did, we still needed a little bit of luck.”