In the second game, Slot plumped for a much stronger XI - almost his first-choice - but saw his go-to men put through their paces by a stubborn and crafty Athletic Club side, managed by Ernesto Valverde.
Mohamed Salah opened the scoring, but Oihan Sancet pegged the hosts back.
Cody Gakpo’s two goals sandwiched an own goal by the Dutchman as the Basque side threatened from set plays, while Salah skied a penalty on an entertaining afternoon on Merseyside.