Celtic boss Martin O’Neill believes a chastening 3-0 Old Firm defeat to Rangers should serve as a major wake-up call to the club’s new recruits.On what proved to be a torrid afternoon at Ibrox, Celtic were hammered by their bitter rivals in the quarter-finals of the Premier Sports Cup.O’Neill picked a team which included four new signings — Sam Johnstone, Kasper Hogh, Camilo Duran and Mika Baur — in the starting line-up.Another three summer signings came off the bench in the second half but Celtic were soundly beaten by a Rangers team who triumphed thanks to two goals from Dan Neil and one from Kevin Kelsy.It was a major reality check for Celtic, who failed to cope with the energy and aggression shown by Derek McInnes’ side.With the teams set to meet once again at Celtic Park next weekend in the league, O’Neill insists the new recruits need to get up to speed and understand the magnitude of the game. Martin O’Neill had no complaints over the final score, admitting that his side were well-beaten‘We were well beaten,’ said O’Neill. ‘The 3-0 scoreline doesn’t hide it, it was a tough afternoon for us.‘We were well in the game early on, even at half time, but they were stronger than us on the day and they deserved to win.‘I thought the first half we didn’t capitalise, we had a couple of really decent chances when we’d broken their press. But on the day, just second best.‘I think there has to be a realisation of how big this game is. It’s so important to the fans, so important to everybody.‘It’s still one of the great fixtures, as mentioned, in European football, if not the world. And people have got to know that. That’s the point. We’ll have to try and learn from it.‘We play next Sunday, we’ve got a midweek game. But it’s a wake-up call.’Asked if the experience would have been a culture shock for some of his new faces, O’Neill said: ‘I’m sure it will be. It was a culture shock for me 26 years ago when I came here, we got smashed 5-1.‘Listen, we were second best. I have to look at myself for a start, then I look at the team. We were second best.‘You can go on, you can win some games, which we’ve been doing domestically and it’s been fine. We’ve found a way to win a couple of matches which were difficult for us.‘But we were beaten today. Did Rangers surprise me? No. I think they’re strong. I think they’re physically strong. So it’ll be a big test for us next Sunday again, in every aspect.’ It proved to be baptism of fire at Ibrox for the likes of summer signing Mika BaurWith no away fans in attendance at any of the Old Firm matches this season, O’Neill believes it will be a different story next weekend at Parkhead.‘I think throughout the first half we, in really good positions, gave the ball away, we had three or four brilliant opportunities on the counter-attack and wasted them,’ he continued.‘Everything Rangers did, I expected them to do. Whatever way Rangers set up, they’re not going to give me a call and say what they’re going to do, so we had to counter that.‘Next Sunday will be a different ball game when we’ve got the home crowd with us and if they make the same sort of noise as Rangers made today that will be very helpful.‘We can learn from this and that’s the most important thing. We need to.‘If you’ve been beaten in the game, you always think about selection. I will think about my own part in proceedings and then we’ll see. I wanted people to experience this atmosphere and they certainly did.’O’Neill insisted that the lack of away fans was not solely to blame for his team’s performance, pointing to the experience of the likes of Callum McGregor and Kieran Tierney.He also insisted that Colby Donovan was one of the few Celtic players to emerge with something close to pass-marks from such a hefty defeat.Asked whether he considered making more than just one substitute at half-time, the Celtic boss replied: ‘Yeah, it could have changed. Me personally, I think young Colby has come out of this with great credit. I think he’s an absolute warrior.‘Sometimes we misplace passes, but he’s got a big heart. I think we can all learn from that. And because of the size of his heart, he was booked in the first half, but he kept going right to the end.‘He was booked against St Mirren after about eight or nine minutes, still kept going. In terms of heart and desire, he’s been a big plus for us.’