Chad told me he was sizing up brad and he thinks he can take him.

Conor was sizing up Jake for their big fight and thinks he can win.

“What’s he doing with the ball”
He’s sizing up seeing how he reacts

Blah blah sizing up just seeing how to react to someone by examining them

“What are you waiting for, get on it”
“I’m sizing up.”

He did size up the potential destruction, but did not act decisively in the end.

"Yo, no long talkin' b. Either size up or nize up"

In other words...

"Hey man, I don't want to do this long talking business anymore. Either stand up to me and let's fight, or shut up."