Ousmane Dembele's strike sent Barcelona three points clear at the top of La Liga with a tense 1-0 win over Atletico Madrid on Sunday.
Capitalising on champions Real Madrid's defeat by Villarreal, Barcelona set out to make a statement victory at the Metropolitano.
Shorn of suspended top scorer Robert Lewandowski, Xavi selected Ansu Fati up front in his place, but it was Dembele who made the difference, finishing a slick move in the 22nd minute.
Atletico ramped up the pressure, with the superb Ronald Araujo clearing off the line from Antoine Griezmann at the death, but Diego Simeone's side could not find an equaliser.
Both teams finished with 10 men after Ferran Torres and Stefan Savic were sent off for brawling with each other on the floor as tempers soured.
Defeat means Atletico languish in fifth, 14 points behind leaders Barcelona.
The victory earns Xavi some breathing room after criticism and fills Barcelona's sails with wind ahead of the imminent Spanish Super Cup in Saudi Arabia.