The README file provides an overview of the FIFA 21 complete player dataset, emphasizing its contents which include data for Career Mode from FIFA 15 to FIFA 21, offering a potential for multiple comparative analyses across these versions. It outlines that the dataset includes over 100 attributes per player, encompassing areas such as player positions, attributes (e.g., Attacking, Skills, Defense, Mentality, GK Skills, etc.), and personal data (Nationality, Club, DateOfBirth, Wage, Salary, etc.).

Given the hint that the 'defending_marking' column is missing in the 'players_21.csv' file, we'll focus on verifying this specific issue by examining the 'players_21.csv' file to check for the presence or absence of the 'defending_marking' column. This investigation aligns with the context and expectations set by the README, which implies a comprehensive set of player attributes should be present in each annual dataset. Let's proceed with examining the 'players_21.csv' file to verify the hint provided.The examination of the 'players_21.csv' file reveals that the column 'defending_marking' is indeed missing. This finding aligns with the hint provided, indicating an inconsistency within the dataset when compared to the expectations set forth in the README documentation, which implies a broad and comprehensive set of player attributes, including defensive capabilities, should be included.

Here is the identified issue in detail:

```json
{
    "issue": "Missing 'defending_marking' column in 'players_21.csv'",
    "evidence": "Column names: ['sofifa_id', 'player_url', 'short_name', 'long_name', 'age', 'dob', 'height_cm', 'weight_kg', 'nationality', 'club_name', ..., 'lwb', 'ldm', 'cdm', 'rdm', 'rwb', 'lb', 'lcb', 'cb', 'rcb', 'rb']",
    "description": "The 'defending_marking' column is missing from the 'players_21.csv' file, despite the README indicating that datasets include comprehensive player attributes (including defensive skills). This omission could lead to incomplete comparative analysis between player attributes over different FIFA versions."
}
```

This issue directly impacts the dataset's comprehensiveness and the accuracy of potential analytics, particularly for those focusing on player defensive skills over the years. It's important to note that this could also affect historical comparisons or trend analyses involving defensive capabilities across different FIFA versions.