It’s not as if
Definition 1 of 1
Pro Tip 1/3Dismissive Tone
Indicates the speaker is dismissing the preceding statement, often suggesting it's unimportant or irrelevant. 
It's not as if your opinion will change the outcome of the game.
Pro Tip 2/3Sarcasm Element
The phrase can convey sarcasm, showing the speaker's doubt or disbelief regarding the preceding clause. 
It’s not as if you’re the first person to ever make this mistake.
Pro Tip 3/3Contrast Stress
Used to stress a contrast between what is true and what is not, sometimes minimizing the latter. 
It's not as if she won by luck; she's trained for years.