A new player could have only dota 1 experience, similar to how I was... and win 7 times, but have 3 losses. The percentage should not matter, he should not be matched with people that are familiar with the game engine with 200+ wins and have played every hero there is to play in dota 2. It took me over 30 games to get used to the engine and transition to dota 2, and I would not want to be matched with a player like that, and I would definitely not want to hinder my team.