Just weeks ago, the 23-year-old completed the Olympic long-course backstroke double in Paris, winning both the 100m and 200m gold medals.
Fenerbahce notched a 5-0 win over Rizespor as Fred's treble helped the Turkish giants to the top of the league with seven points in three games.
Magnus Carlsen had accused Hans Niemann of cheating after the American beat him at the 2022 Sinquefield Cup.
Tatum, a member of the USA's gold-medal winning squad at the Paris Olympics, added that heading into the new season as NBA champions was a "different" feeling.
Sunday's match at Atletico's Estadio Metropolitano was halted for 15 minutes after home fans threw objects including lighters at Madrid players.