maybe because he is pro?:)

I understand what you're saying and yes it makes sense, but stopping the analysis there is leaving the question only half answered and leads to an absurd conclusion.

Yes, a player change can make a team more unpredictable because now obviously another player will be taking that spot, but this is also making the team inherently weaker. And I'm not talking about chemistry, I'm talking about playing with four other players for hours every single day for months. You can replace one of them for a stronger player with whom you also have great chemistry, but at least initially you're bound to underperform because you don't know their style. It works both ways. Training isn't simply about learning to aim or working through your strats a bazillion times, it's about playing as a team.

You don't hear SK or fnatic saying: "Oh thank god Na'Vi isn't attending with a stand-in - we'd stand no chance!"

What you hear is things like mouz not making it through the group stage? Why? They recently replaced two players. Same with Winfakt. They said that they performed well DESPITE roster changes.

Why is ESC potentially the best CS team ever? Because they've (-1) been playing together for a decade. It's not making them weaker, it's making them stronger. By your argument, other teams should know each one of them inside out by now, but they don't. And ESC aren't exactly a head above everyone else when it comes to individual skill (Neo's the exception obviously).

Oh and as far as those mixes winning stuff go, yeah it happens. Anybody can have a good day, anyone can have a bad day, anyone can get lucky, etc. CS is like football, or like any other sport. There are some real sick aimers out there, not just those playing in top 10 teams. When you're hitting your shots, anything can happen.