The BCCI might have had the following logic 1. Ganguly as ODI captain: First he does not deserve a place in team itself due to his poor running between wickets and fielding. 2. Tendulkar: Who might have refused 3. Yuvi: Is a head weight. It is generally thought Dhoni has a better captaincy acumen than Yuvi. 4. Shewag: Out of form for a long time. So they are left with choice of Dhoni as there was no alternative. Under the circumstances this was the best decision.
