Celtic boss Martin O’Neill admitted his summer recruits need to prove that they have the character and quality to handle the pressure of playing for the club.The league leaders went down 2-0 at Falkirk on Sunday afternoon – their sixth defeat in their last 10 in all competitions – as they missed the chance to extend their advantage at the top of the Premiership table to seven points.First-half strikes from Ethan Ross and Scott Tanser had the Bairns ahead at the break, and despite peppering Scott Bain’s goal in the second period, the visitors were unable to find a response.When it was put to O’Neill that some new members of his squad are still struggling to meet the club’s high expectations, he said: ‘Absolutely. You have to cope with the pressure to be a player.‘Tommy Burns said it might be easier to play against Celtic than for Celtic but hopefully we have enough in the dressing room and players who have been big winners.‘When you ask managers sometimes you think the best team is the one that has won convincingly, but there are a number of players who have arrived. Celtic manager Martin O’Neill was unhappy with his team’s defending at Falkirk‘You can think someone is doing well in training but the only place to find where players fit is out there.‘We’re not used to losing a lot of games. We were in a much worse position this time last year so we have to buckle down and win a game and win a game in Europe. Thursday [against Besiktas in the Europa League] is a big game and then the following Sunday is massive before we go into the international break.‘We need to sort out a few things. I was asked about confidence. If you take Kasper [Hogh], he wanted to get a goal after some time.‘Something might fall for him but it’s not just that something might fall for you. You have to work at it which is something us as a team and the players in particular need to do.’O’Neill bemoaned the defensive lapses that allowed Falkirk to open up a two-goal cushion, but saw enough in his team’s performance in the attacking third to give him confidence that things will soon start clicking.‘I’m naturally disappointed to have lost the game,’ he said. ‘We had a lot of chances. Their goalie was magnificent but naturally we’ve lost so I’m very disappointed. Callum McGregor looks frustrated as Celtic are made to suffer in Falkirk‘The goals were very poor from our viewpoint. We didn’t clear it for the first one then we let someone run through and pick his spot for the second. We had some really great chances we just weren’t able to convert.‘At half-time I thought we were still in the game. I thought we’d played decent stuff. If you concede a magnificent goal you take it in your stride.‘When you concede a bad goal, which from any viewpoint was a poor goal, then it’s tough to come back then the goalie makes some saves and it’s frustrating.‘Despite mistakes at the back we had enough chances to get back.‘We have conceded some poor goals and haven’t kept a clean sheet for some time which is the essence of a championship team, but we’re still top and we need to address it and that’s the way out of it.‘We scored seven against Hearts which isn’t that long ago. I just thought the goalie had a magnificent game and we should have scored a number in each half.‘When you don’t it becomes frustrating. We have to address that we were conceding. Hopefully we can still do that. It’s still a long season.’