The current defensive structure at Chelsea is one of the most well-established in English football, with both defenders and midfielders playing a key role in the team's success.

However, there have been concerns about the team's overall defense over recent seasons. Injuries to key players such as Mason Mount and Joe Hart have put pressure on the defense to improve its defensive solidity.

Furthermore, Chelsea has struggled to find consistent goalscorers, which has affected their attacking performance. This lack of goals has led to frequent losses in matches against top teams.

In response to these issues, Chelsea has implemented several changes this season. The club has brought in new defenders from different countries to help strengthen the defense. Additionally, they have strengthened their midfield by bringing in experienced players like Victor Wanyama and N'Golo Kante.

However, despite these improvements, Chelsea still faces some challenges in securing their defensive stability. They need to ensure that their defense remains strong enough to stop opponents from scoring goals while also limiting the damage caused by injuries.

Overall, Chelsea's defensive structure is one of the most important aspects of their game. While they have made progress in recent years, they still face significant challenges in maintaining their defensive stability. With proper management and training, it will be possible for Chelsea to continue to develop and improve their defensive abilities.