Lionel Messi's first-ever goal against Chelsea earned Barcelona a 1-1 draw on Tuesday and a slender advantage in their Champions League last-16 tie.
Messi capitalised on a late mistake by Andreas Christensen after Willian had given Chelsea the lead to make Barca slight favourites to reach the quarter-finals.
Paulinho started ahead of Ousmane Dembele for an otherwise-full strength Blaugrana against Chelsea, who went with ex-Catalans pair Pedro Rodriguez and Cesc Fabregas.
The two sides had an illustrious history of facing one another, although the Blues most recently beat Barca en route to winning the Champions League in 2012.
Ernesto Valverde's troops saw more of the ball in the first half but were lucky to go into the break still goalless as Willian struck the woodwork twice with two shots that hit either of Marc-Andre ter Stegen's posts.
The Brazilian went one better on the hour mark, receiving a short corner, before shifting to his right and curling a fine effort into Ter Stegen's bottom corner.
However, Barca's switch to a 4-3-3 formation, coinciding with the introduction of Aleix Vidal, opened the game up for the visitors, and they made Chelsea pay for their only defensive lapse.
Indeed, Andres Iniesta dived on to Christensen's suicidal ball across goal and cut back for Messi, who ended his drought against the English champions ahead of the second leg on March 14.
Chelsea 1-1 Barcelona
Willian 62 (C) Messi 75 (B)
Chelsea: Courtois; Azpilicueta, Christensen, Rudiger; Moses, Kante, Fabregas (Drinkwater 84), Alonso; Willian, Hazard, Pedro (Morata 83)
Barcelona: Ter Stegen; Sergi Roberto, Pique, Umtiti, Alba; Rakitic, Busquets, Iniesta (Gomes 90); Paulinho (Vidal 63); Messi, Suarez
Referee: Cakir (TUR)