Barcelona survived Gerard Pique's red card to register a 3-1 victory over Olympiakos in the Champions League on Wednesday.
Pique picked up a second yellow for handball just before half-time, but Lucas Digne and a Lionel Messi free kick ensured it was business as usual for Barca, who stayed three points clear at the top of Group D.
Jordi Alba was missing for the Catalans, who reverted to a 4-3-3 formation. Olympiakos, meanwhile, lined up with Spanish defender Alberto Botia, who began his career with the Blaugrana and also turned out for the likes of Sporting Gijon and Sevilla.
The Greek side had won their domestic League in all-but-two of the last 19 seasons but lost three consecutive games before bouncing back over the weekend.
Wednesday marked the first-ever meeting between the two sides in the Champions League, although Barca boss Ernesto Valverde previously coached Olympiakos twice.
Gerard Deulofeu’s early corner was flicked on by Samuel Umtiti to Luis Suarez at the far post, but the striker couldn’t slide his finish on target from a couple of yards out.
Moments after Paulinho blasted a shot just over, Nikolaou miscued his clearance on the end of Deulofeu’s cross, diverting the ball into his own net to give the Blaugrana the lead.
Deulofeu was at it again, easing past Leonardo Koutris and hitting a low shot on target from the right, which Silvio Proto tipped over.
Andres Iniesta then played a deft one-two with Messi, before cutting back for Paulinho, who tucks the ball away from close range, but the Spaniard was just offside.
Barca looked to make it 2-0 when Iniesta picked out Paulinho with a delicious cross, but the Brazilian’s header smacked against the woodwork and bounced clear.
The attempts kept coming as Proto deflected Suarez’s close-range finish wide, before blocking Messi’s low shot from the right.
Yet Pique risked throwing away all of Barca’s dominance just before half-time as he used his brush in a rebound, resulting in his second yellow card and Barca going down to 10 men.
Barca were understandably less adventurous after the break, but their grip on the game didn’t wane as Messi bent a free kick into the roof of Proto’s net for his 100th goal in Europe.
Digne soon made it 3-0, firing an angled drive into the bottom-right corner of the Belgian’s net after Messi’s cutback fell his way.
Proto went on to deny the No 10 and Paulinho in quick succession, but Olympiakos did grab themselves a consolation at the death, when Nikolaou jumped highest to power a header past Ter Stegen from a corner and make amends for his earlier own goal.
Barcelona 3-1 Olympiakos
Nikolaou og 18, Messi 61, Digne 64, Pique sent off 42 (B) Nikolaou 89 (O)
Barcelona: Ter Stegen; Sergi, Pique, Umtiti, Digne; Busquets (Gomes 80), Paulinho, Iniesta (Rakitic 67); Messi, Suarez, Deulofeu (Mascherano 45)
Olympiakos: Proto; Elabdellaoui, Botia, Nikolaou, Koutris; Gillet (Djurdjevic 55), Romao, Zdjelar; Carcela (Pardo 65), Odjidja-Ofoe (Fortounis 71), Androutsos
Referee: Collum (SCO)
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