A Team or an individual does not perform well.
Who do you think is responsible.
The team member(s) or the Leader.

I think the responsibility comes from top to bottom – So does lot of other things (appreciation, power, salary etc.)
You cannot always put all the pressure of performance on the team.
There can be various reasons why a team is not performing.
And I think it’s the job of the manager or his leader to understand why this is happening and come up with a solution.

No doubt, firing can be one of those solutions, but you should have given ample time and taken all the circumstances and choices of that individual into perspective before you do that.

It’s a failure at the manager’s end also, if you are firing somebody, it also means that you were not able to motivate or lead that person (apart from all other performance reasons)

Again it’s easy said than done. However you just learn from your experiences and make sure you don’t do the same mistake again.

“A smart man makes a mistake, learns from it, and never makes that mistake again.”