The Ultra Athletes archetype is a deck centered around many different sports, with the main gimmick being able to swap out cards from your field to your hand, similar to subbing in and out players in an actual sport. The deck focuses on putting out offensive cards on your turn to do battle with and then switching them to defensive cards in your MP2. Lets go over all the U.A. cards you can consider.
U.A. Libero Spiker
One of the two Normal Summonable U.A Monsters, Spiker will be your Normal Summon for most of your games, or what you will be searching in the event that you do not have a Normal Summon. It's first effect allows us to summon him out by returning another U.A monster to our hand. Every U.A monster has this effect with one exception, which I will mention later. The second effect allows us to return one Level 5+ U.A. from our hand to Special Summon out a different one on our opponents field. Keep in mind that it does not have an activated effect you can use on your turn.