Reference

At the start of the 2005-06 season, Celtic faced several significant challenges before Shunsuke Nakamura's debut:

1. European Misfortune: One of the biggest blows came early in the season when Celtic lost 5-0 to Artmedia Bratislava in the first leg of the UEFA Champions League second qualifying round. This result was a massive setback and an early sign of the struggles they would face (source).

2. Managerial Transition: Gordon Strachan had recently taken over as the manager, succeeding Martin O'Neill. This transition brought about a period of adjustment and restructuring, which naturally comes with its own set of teething problems (source).

3. Squad Overhaul: Strachan was in the process of rebuilding the squad, which included bringing in new players like Nakamura. This period of rebuilding often means integration issues and finding a balanced team dynamic, which can affect early-season performance (source).

4. Domestic Upset: The team also faced disappointment in domestic competitions. For instance, Celtic drew 4-4 against Motherwell on the opening day of the season, which was seen as a poor start to their league campaign (source).

These challenges combined made the start of the 2005-06 season particularly testing for Celtic before Nakamura's debut. However, despite these early difficulties, Nakamura's arrival soon brought a positive impact, helping the club to regain its footing in the subsequent matches. Here is an image of Nakamura: