On that occasion, back in 2005, Sergeant was manager at the Millennium Stadium, when 61,569 fans turned up to see the Lions draw 25-25 with Argentina in the Welsh capital ahead of their trip to New Zealand. The crowd won't be as big on Saturday night, but the occasion will be much bigger.
"I've been in Melbourne for eight months now and everyone who is still here at the Etihad from 2001 refers to the last game against the Lions being the best event they've ever staged," said Sergeant, made OBE in 2007 and five times the International Venue Manager of the Year.
"They are very excited to be having the Lions and their incredible fans back at the ground and we are all looking to turn into a fantastic fan experience. We'll have the roof closed and I hope we can encourage all the Lions fans to sing their hearts out.
"I went to the first Test in Brisbane with my 11-year-old son and the atmosphere was terrific. But I was hoping to hear a little more singing from the Lions fans - that's something we simply don't hear in Australian sport.
"I know the Lions fans have been split up into small groups and dotted around the various stadia so as not to give them the chance of gathering in a huge group as in 2001, but if we could just get a few lines of Delilah, Fields of Athenrey or Flower of Scotland going it would be great."
Sergeant's event management style has taken him to top jobs at many of the world's leading stadia. His global success has largely been based on building business by focusing his best efforts on giving the fans the best possible match or event day experience.
Over the past 30 years he has held senior positions at Wembley Stadium, the Millennium Stadium, Suncorp Stadium in Brisbane and the Allphones Arena in Sydney. In that time he has managed more than 3500 major events and projects including FA Cup finals, FIFA World Cup Qualifiers, Tri-Nations Rugby, Rugby League World Cups and Bledisloe Cup, along with concert tours including Michael Jackson, Madonna, U2, Pink Floyd, Oasis and Guns 'n' Roses.
"We're very lucky in Melbourne to have so many magnificent stadia in the city, but then you have to remember the population of Greater Melbourne is just over four million people - a million more than in the whole of Wales," added Sergeant.
"The playing area at the Etihad Stadium is three times the size of the Millennium Stadium and we have up to 80 major matches a year taking place here. We have four resident AFL clubs, Essendon, St Kilda, Carlton, North Melbourne and Western Bulldogs and we also host games for the Melbourne Victory soccer side.
"We have a resident Big Bash cricket league team, the Melbourne Renegades, and we've also hosted rugby league and rugby union. The stadium was built as a catalyst in the heart of Melbourne's old Docklands area and those Lions fans who were here in 2001 will barely recognise the area.
"It has become so built up around the stadium now that we'll soon have 30,000 office workers and 60,000 residents virtually on our doorstep."
The Lions headed to what was then the Docklands Stadium 12 years ago in the same position they are in this weekend having won the first Test in Brisbane. They led at half-time in Melbourne before going on to lose by a record 35-14 margin. They then lost the third Test in Sydney, and their first series to the Wallabies.
But Sergeant, whose Australian wife is cheering on the Wallabies while he is sticking to his English roots, believes the Lions have two secret weapons in their side that can tip the balance in their favour.
"When I was chief executive at the Scarlets I had to sign the first contracts for two talented youngsters. Now they are both in Melbourne with the Lions - Jonathan Davies and George North," recalled Sergeant.
"We all saw what they are capable of in that first Test and George's try would have raised the roof if they had had one at Suncorp! It is great to see how much they have developed."
As well as staging the second Test, the Etihad Stadium has also staged a special night for the Lions fans and is offering them a 'Hair of the Dog' package at an AFL game on Sunday.