You mean PR? If I am good, than he was in the same group with Thor and Fabian. Hushovd was the leader, he was going to win that race. Imagine the situation, first you are with Cancellara, your teammate is ahead. You start to help to Fabian, and when you are enough close to Vansummeren and you are leading and Cancellara attacks from behind than you never catch him again because its surprising, and you already tired of chasing down your teammate, and he going to win the race. On the second situation you are with other riders, including one of your helper and Canc etc. You know that you are faster than Fabian, and in this situation you have a very good chance to win the race if you catch Vansummeren. And no need to get yourself tired, and also you can watch Cancellara.
Enough?