Martin O'Neill's quadruple-chasing side today embarked on a gruelling but thrilling 12-day period which would shape the rest of their season.
But nobody inside the Celtic dressing room at least was looking ahead to next week's UEFA Cup 'Battle of Britain' with Liverpool or the CIS Insurance Cup final against Rangers.
First the defending champions, with a game in hand, were looking to peg back the six-point deficit on their arch-rivals at the top of the Scottish Premier League.
So much was on the line with Celtic seeking revenge for the 3-2 defeat at Ibrox in December and O'Neill was quietly hoping to end Alex McLeish's Old Firm hold over him as he remains unbeaten in the six matches since talking over the Rangers hot-seat.
McLeish's plans were hit before kick-off in the intimidating cauldron of Parkhead with Dutch international Ronald de Boer losing his battle to recover from a calf strain.
Arthur Numan was already ruled out with an ankle injury, but Rangers were boosted with the news that Old Firm specialist Peter Lovenkrands returned after shaking off a back problem.
McLeish made two changes from the team which beat Livingston last week with the Dane replacing Michael Mols and Maurice Ross coming in for Kevin Muscat.
But Celtic were still without Henrik Larsson, who was waiting to get the go-ahead for a comeback after suffering a double fracture of his jaw a month ago.
O'Neill made three changes to the Celtic team which beat Hibernian in the last minute thanks to a goal from Johan Mjallby, who stayed in the starting XI.
Bobo Balde and Chris Sutton had recovered from hamstring strains and goalkeeper Robert Douglas came in with Stephen Crainey, Shaun Maloney and Javier Sanchez Broto missing out.
Celtic: Douglas, Mjallby, Balde, Valgaeren, Agathe, Lambert, Lennon, Petrov, Thompson, Sutton, Hartson. Subs: Broto, Sylla, McNamara, Maloney, Crainey.
Rangers: Klos, Ross, Moore, Amoruso, Bonnissel, Ricksen, Arteta, Ferguson, Lovenkrands, Arveladze, McCann. Subs: McGregor, Caniggia, Malcolm, Konterman, Thompson.
Referee: M McCurry