Barcelona had last tasted league defeat 13 months ago against Malaga, going 43 games unbeaten, but they failed in the 37th match of this season to tarnish an otherwise flawless domestic campaign.
Barcelona lost 5-4 in a wild game at Levante on Sunday, ruining the champion's chance to become the first team to finish a Spanish league season without a defeat under its current format.
Real Madrid did not need resting forward Cristiano Ronaldo to crush Celta Vigo 6-0 at home in its second-to-last match before the Champions League final against Liverpool.
Barca are two matches away from becoming first team in La Liga since 1933 to complete a season without losing and first since league was expanded from nine teams.
Sergi Roberto will miss the rest of the Liga season and the first match of the next campaign after being given a four-game ban for striking Real Madrid's Marcelo in last Sunday's tension-filled 2-2 draw at the Nou Camp.