It was a feat the defender also managed to repeat the following season as Gordon Strachan's side punched well above their weight in Europe once again to finish in the top two of the group section and qualify for the last 16.
Now, at the halfway point in their Champions League group campaign, Neil Lennon's Celtic are in a healthy position to become the first Parkhead team since then to make it into the knockout stage of the competition.
After starting their Group G campaign with a draw at home to Benfica, the SPL champions became the first Parkhead team to record a victory on the road in the competition when they travelled to Russia and defeated Spartak Moscow 3-2.
During the week, Lennon came agonisingly close to watching his team earn a shock share of the spoils at the Nou Camp against Barcelona until a 94th-minute winner from the Spanish giants broke their hearts and inflicted a 2-1 defeat on them.
But, with two homes matches from their final three group encounters – against Barca and Spartak – McManus believes the Parkhead club still have every chance of causing an upset by landing second place in the group behind the Catalan giants.
"You would have to say Celtic are in a reasonably strong position," said McManus, who is currently on loan at Bristol City from Middlesbrough.
"I'm sure if you had said to Lenny that by the halfway stage Celtic would have taken four points from the first three matches, and played as well as they did over in Barcelona, he would have taken that.
"There is such a fine line between success and failure at Champions League level that you just wonder if not managing to hold out for a point at the Nou Camp, which would have been an incredible result, might come back to haunt them.
"But everyone knows just how special the atmosphere at Celtic Park on European nights is, and that will give the players a huge lift going into the two home matches.
And if the previous two away displays are anything to go by, then they will also be difficult to beat at Benfica.
"So, as much as it will still be extremely difficult, you would have to say Celtic are certainly well in the mix."
McManus was unable to watch the Nou Camp clash live on Tuesday night as he was playing for City, but he watched the game when he returned home and was highly impressed with the way the Parkhead players went about their business.
In particular, the defensive partnership of Efe Ambrose and Kelvin Wilson caught his eye as they managed to keep some of the best players in the world, perhaps the greatest of all time in Lionel Messi, relatively quiet.
"You hear people saying you can't switch off for a second and that really is the case when you are playing at that level," said McManus.
"These guys look as though they aren't interested and a split second later they have managed to spin in behind you. You need to be on your toes at all times.
"I remember playing next to Gary Caldwell and it is vitally important you are constantly communicating with each other and passing your man over at different times because the movement of these players is unbelievable.
"And, at this moment in time, there aren't many teams better at that than Barcelona. Their players all seem to have the freedom to go anywhere on the park and that can make it difficult in itself because you need to make a call on whether to follow your man or stay in your position.
"Fraser Forster was just excellent and you need your goalkeeper to have those sort of nights when you are playing against the top teams."
HE ADDED: "The two central defenders played really well. That is the first time I've watched Ambrose and he was excellent, as was Wilson.
"But Celtic defended really well as a team. Scott Brown was coming back and helping out on the right and Charlie Mulgrew was doing the same on the left. It was a real team effort and hopefully they will take a lot of confidence from the overall performance."
McManus was particularly pleased for his former team-mate Lennon and says he has already shown he can become a leading manager.
He said: "Everyone who played in the same team as Lenny and shared a dressing room with him, knew he would move one day into coaching or management.
"He is still learning, but he is doing a great job for Celtic. I think he is the sort of manager a player would enjoy playing for and you can see that from his team's performances; they are giving it everything.
"As I said, it will still be very difficult to qualify, but they have given themselves a fighting chance – and that is all you can ask."