Arsenal boss Mikel Arteta has explained why Jurrien Timber and Riccardo Calafiori were left out of his starting XI to face Club Brugge in the Champions League on Wednesday night. The Gunners were already without key defenders Gabriel and William Saliba due to injury, meaning midfielder Christian Norgaard was handed a surprise start in central defence in Belgium.Arsenal have had a very strong start to the season but have seen key players pick up injuries in recent weeks, particularly in defence. Gabriel, William Saliba and Cristhian Mosquera  have all been sidelined, while Leandro Trossard and Declan Rice were also ruled out of the trip to Belgium for Arsenal's latest Champions League match. The situation means that Arteta raised a few eyebrows with his team selection against Club Brugge as the north Londoners aim to maintain their 100% record in the competition so far this season.The Arsenal boss told TNT Sports ahead of kick-off: "They both had issues from the weekend, both really bad kicks. For Jurrien it was too early and for Ricci [Calafiori] we have to manage to see if he can do some minutes [tonight]."The absence of the duo meant that Arteta lined his team up with Norgaard partnering Piero Hincapie in central defence, with Ben White and Myles Lewis-Skelly as the full-backs. The outing is Norgaard's first as a centre-back since featuring in the role for Brentford in the Championship back in 2020.Looking for smarter football bets? Get expert previews, data-driven predictions & winning insights with GOAL Tips on Telegram. Join our growing community now!Arsenal have now suffered 28 injuries already this season, but Arteta has defended his training methods and insists they are not to blame.He told reporters: "Not training, no, because we don't have time to train. So, training is not there. But obviously, the fact that you are missing players, you are loading other players more. That's a consequence of that and it's a really dangerous. The fact that we have some others who have long-term contracts that haven't been with us since the beginning of the season. But, yeah, it's a test for the team, and so far, we have reacted very, very well to that.""I think you have to separate the kinds of injuries that they have. Some of them have been long-term and acute injuries, especially with some of the key players who give you a lot of days out. It's something that we are constantly looking at. As I said, we have played a lot of games with a lot of players missing. That gives a lot of stress and then more injuries. We are on it and I'm really happy with what we are doing in terms of the medical stuff and everything that we are trying to do together. Sometimes, as well, we need some people to go in our time."It's not only one season. It's about some of the players that they have played. It starts to get overloaded and you start to ask them again and again to play. Others, because, as well, the moment that you have an injury, you are more likely to have another injury. That's been a consequence of some of the states as well. We're on it."Arteta also took time out to praise Norgaard pre-match. The summer signing has only made two appearances as a substitute in the Premier League so far this season and just one start in the Champions League. Yet Arteta is happy with how he's settled in following his transfer from Brentford. He told reporters: "I'm really happy with how he’s come to the club, especially with him and everything that we need to do in many areas. Not only in the pitch, but what he has to do, he excels in the manner that we expect him. I think it's similar to Ben White or Myles [Lewis-Skelly]. They haven't played as much as expected, but they're very positive."Arteta will be hoping that the injury situation does start to clear up ahead of hectic run of fixtures over the festive break. The Gunners play Wolves, Everton, Brighton and Aston Villa in the Premier League and also face an EFL quarter-final against Crystal Palace before the end of the year.