Well, I see it in the same way of Litotes. I bet on the players that have an odd (that is relates to the chances that he has to win) that, in my opinion, has to be lower than it is. Betting for me is like wasting credits in players that I think that have better chances to win than the chances that vBookie (in MTF) says.
Af course if I think that Granollers has a 20% of possibilities to win I won't bet all my money in him. For this kind of bets the correct way is to spend a little amount of credits. If you guess the outcome of the match, as the odd is very high with little amount of credits you can win a lot of them, sometimes more than betting all your money in one favourite player.
The key is mixing "safe" bets and this kind of bets that we are talking about (in my opinion). And making a good management of the amount of credits for each pick. Here in MTF I bet almost all my money every day because I want to be in 1500 - 2000 credits to start an efficient management (if I'm lucky too