Dictionary out of range

Question

I am getting an index out of range error, when I initialize the TValue to 10. So the elements should exist.

 if (!sportsDictionary.ContainsKey(sports.Team))    
 {        
      sportsDictionary.Add(sports.Team, new List<SportsObject>(10)); 
 }     
 else    
 {         
      sportsDictionary[sports.Team][Team.sportsId] = sports; 
     //Error: index out of range above
 }