It was the first time Barcelona had lost at home in LaLiga since their defeat to Alaves in September 2016, 793 days ago.
The Argentinian came close to scoring in the opening minute but failed to properly connect with the ball and Betis quickly asserted themselves, seriously challenging Barcelona for ball possession, the rarest of sights for opponents at the Nou Camp.
Dembele was not in the Barcelona squad that lost 4-3 at home to Real Betis on Sunday, with reports surfacing he had breached team rules. Ousmane has been starting games recently but right now he is not in the squad.
"Ousmane has been with us for a while", Deschamps said in a news conference on Monday when asked about the player's toils at Camp Nou.
However, the expected fightback didn't eventuate as Giovani Lo Celso restored Betis' two goal lead just three minutes later.
Espanyol could jump both and move level on points with the Catalans when they visit Sevilla later on Sunday. Quique Setien's side may have pulled back on the sumptuous, attacking football that earned them a sixth-place finish last term but, in full flow, they remain one of Spain's most hard opponents to stop.
Barca coach Ernesto Valverde took off midfielder Arthur for Vidal at the start of the second half to give his side more dynamism but they continued to leak chances and Betis showed no remorse. He missed the morning training and what the club has blamed us for is that he did not provide notification so a doctor can come to assess him.
Betis seemed faster, sharper and hungrier while Barcelona's midfield was repeatedly carved open on the break.
Joaquin Sanchez made it 2-0 for Betis before halftime.
Messi recorded his first strike of the day from the penalty spot in the 68th minute, helping to half Betis' advantage at that stage. Two substitutes combined for a second, Munir El Haddadi laying on Vidal to make it 3-2 but no sooner had the recovery began again, it was halted.
They say Klopp is a huge fan of the winger - and the German feels Dembele could help Liverpool win their first Premier League title.