A shot in the locker old-fashioned noun phrase
Having only one chance left one can do in order to achieve something
This is a shot in the locker. I can't screw it up.
It's very intense right now! Peter has a shot in the locker.
Don't lose hope! You still have a shot in the locker before everything goes south.
The last opportunity for one to achieve something
To be outperformed or outrun by someone, usually by a very wide margin.
You have to be quicker to finish this task or you will eat other my dust.