THE big question was resolutely answered yet again by Celtic.

Not that Callum McGregor ever believed his team would not show themselves to be strong enough, both mentally and physically, to reach another cup final.

For almost two and a half years, Celtic have returned from a trying and tiring European match and faced within days a significant domestic test, be it games against the top teams, or finals and, as with Sunday, a semi-final.

Not once have they faltered. Sunday was supposed to be Hearts’ day and yet once Scott Sinclair scored from the penalty spot, the outcome of the Murrayfield match was never in doubt.

McGregor has played in just about all of the games which have come directly after a Champions League and now Europa League tie, Celtic were in Leipzig on Thursday, and still the side top of the league were eventually easily beaten.

Celtic are in Norway to play Rosenborg three days before facing Aberdeen in the Betfred League Cup final, another challenge, but so far the travel and torment of a defeat, which has often been the case, has had no lingering affect on this group.

It's why a third Treble in a row is very doable.

McGregor said: “It was another big game for us on Sunday and it was a case of, ‘can we go and do it again?’ I think we answered that. We were outstanding in that second half. We passed the ball, created numerous chances and it could have ended up four or five.

“It is important we start games better but semi-finals are always nervy with teams not wanting to give too much away. Once we clicked in to gear we dominated.

“We've always bounced back from the European game. That’s a big part of being at Celtic. It’s a step up when you play in Europe but it seems to often to be the case that we come back to big games, like semi-finals and finals.

“We have learned we can’t be too disappointed when we have massive games just a few days later. Five finals out of five is incredible and it shows the character of this team We have the strength to bounce back.

“It’s a great record we have in the big games and it’s testament to the lads. Our guys go and show why they are top players.”

It is Aberdeen again for Celtic who won their first treble under Brendan Rodgers beating the Pittodrie men twice in the two finals that season.

It could have been Rangers, and you get the feeling McGregor and Co would have liked that, but instead Celtic face a team they’ve had a lot of joy against in recent times.

McGregor said: “We’ve not had an Old Firm final for a good few years so it would have been incredible to be involved in that.

“It’s Aberdeen again though and it’s a tough game. We have a good record against them in finals in recent years. It’s great to call on that experience. You always remember those results and it can give you and edge going in to the next one.

“The deserve to be in the final and on their day they are a match for anyone.

“But we’ve been there before and we’ve managed to win leagues and cups along the way, so hopefully we can get another one. We have to prepare properly to arrive at that game with confidence to make sure we get the job done.”

Olivier Ntcham is never going to lack in the self-confidence department and despite the Frenchman not having his best game in Germany, and hurting his hamstring at Murrayfield which kept him in the dressing room at half-time, the midfielder was brimming with hubris about what his team can now achieve.

He said: “The key is simply just to keep going. When we lose we have to go out and become winners again. You have to look forward because we have so many games to play that, if we start looking back, we will be in trouble.

“I think the best team won on Sunday so I am happy for the team and happy to be in the final again. We respond positively when questions are asked and we do that as a team because we are all together.

“We win like that and we are also together when we lose. It was very important to beat Hearts because we play them again on Saturday and this was a good message for us to send out to them. his will put a lot of doubts in their minds because, when you lose 3-0, next week they are not likely to play like they were playing before this game.

“I think we could have scored even more goals but we are improving and it was a positive message when you think of all the players we were missing. It’s always nice to win like this – the first half was difficult for us but we showed our quality in the end.”

Celtic have now beaten Hearts, Rangers, Aberdeen, Hibernian and Livingston, the top teams so far. Kilmarnock remain something of a bogey team.

The fear for every team in the Premiership is that the champions may have already had their one bad patch in the league.

Ntcham added: “Hearts beat us at the beginning of the season and that was our motivation. This was a good game in which to show them that we are the champions.

“Everyone is close to us but it’s always good to show our quality and determination. When we are at our best, though, I don’t think there is anyone here who can beat us.”