The Pittodrie side certainly can’t afford to dwell on the setback. They have eight games coming up in December alone starting with the tricky trip to Ibrox this weekend.
With Aberdeen otherwise occupied, Rangers took the opportunity to move ahead of them into second place on Saturday with a 2-1 win over Partick Thistle.
Jack acknowledged: “Everyone will be saying, ‘oh how are Aberdeen going to react, how’s the team going to be, will everyone be together?’ Of course we are. This is as tight a group as I have ever been involved in. I have no doubt when we turn up at Ibrox come 3pm we will be ready for kick-off and ready to put things right.
“The season is not over,” the Aberdeen skipper stressed. “We are just about to go into December. We have eight fixtures in December. So after December, in the new year, that is when your season normally shapes up and you see where you are in the league, and how you’ve done in cups.
“We have got ourselves to one cup final. Okay, we have had a disappointment, but it’s back to league football and we will look to try and get as many points on the board as we can in the next month.
“I am sure for this team there will be plenty more days like this in the future. Especially with the manager we have because he believes in doing well in the cups.
“There’s still a Scottish Cup, there’s still big games coming up in the league. It’s about dusting ourselves down and staying together.”
Jack admitted Aberdeen’s midfield did not cope as well as they would have liked with Celtic’s strengths in that area. Scott Brown in particular shone and won several 50-50 challenges.
“I think me, Kenny (McLean) and Graeme (Shinnie) did all right in midfield,” he said. “We are all honest enough to say that the way the game panned out, Celtic go two up and they get their tails up and everyone wants the ball, and it makes it more difficult for us.
“It’s just about sticking together, battling away. We all battled away together. Maybe when we got the ball, it might have been better. We know we didn’t quite hit the heights today but we will be back to put that right.”
Kenny McLean, meanwhile, explained the thinking behind Aberdeen’s response to the pre-match Celtic huddle, the Pittodrie players facing up to their opponents by standing in a line with arms around shoulders.
It was a defiant act that deserved to be followed by a better performance.
“Usually we will stand and wait on Celtic, teams will try to keep themselves warm while they do the huddle but we thought we would just stand there,” explained the Aberdeen midfielder.
“It was a final, we were always going to be fired up anyway,” he added. “We had 22, 23,000 fans or whatever it was travelling down. They got us fired up plenty enough and we got ourselves fired up in the dressing room. It just wasn’t to be today.”