Liverpool captain Virgil van Dijk is looking for the team to use their Champions League return to bounce back from the "unacceptable" defeat to Nottingham Forest.After spending last season in the Europa League, Arne Slot's side return to the new format of UEFA's elite club competition with an opening encounter against AC Milan on Tuesday.Van Dijk hopes it will give them a chance to quickly put their first loss of the campaign behind them."We have a very good group that really understand that it was unacceptable and are disappointed," he said of the Forest loss."We all know everyone can do better and we have to show that on Tuesday and that is what we focus on."We have been through losses and difficult moments together and I think we have to stay calm and we will stay calm."Hopefully if there are no injuries happening then rhythm is always a good thing."We need the whole squad and we know after the international break it will be a game every three days so we need everyone in their best shape and best form."Asked whether what they had to do to prevent the defeat impacting their early-season momentum he added: "Keep going and keep working and make sure the performances don't go in that direction."We all know how the atmosphere can change but that is also part of the influence from outside which could affect you."I can't wait to be out there hearing the Champions League tune and leading out the boys."A club like Liverpool needs to be in the Champions League and we are finally back and let's go out there and put in a much better performance as it is needed otherwise you are going to have an issue." Watch Celtic v Slovan Bratislava in the Champions League on Wednesday from 7.30pm on RTÉ2 and RTÉ Player.