If you want to play independently outside of Career, just go to the main menu and select "Play."

In Play mode, you can choose from 1on1, 1 on 1 with Weapons Allowed, Tag Team, and Tag Team with Weapons Allowed. All these modes will have you competing against the CPU.

On the player selection screen, you have the option to choose both your Superstar and the opponent's. Alternatively, you can click the dice icon in the lower right corner of the screen for a random player selection.