Barcelona were held to a goalless draw by a stubborn Olympiakos side as they edged towards qualification for the knockout stage of the Champions League.
Luis Suarez hit the bar with Barca's best chance but the La Liga leaders couldn't break down Olympiakos and had to settle for a point.
Some poor Olympiakos defending saw Lionel Messi go close early on, the Argentinian having his shot saved awkwardly by Silvio Proto, while Luis Suarez's near post poke went comfortably wide.
The home side were starved of possession and opportunities. but striker Kostas Fortounis could have done better when placed on the edge of the box, blazing over under pressure from Barcelona defenders.
He was played through on goal moments later but saw his half volley stopped by Marc-Andre ter Stegen, who grabbed the ball at the second attempt after an initial spill.
Olympiakos continued to frustrate their visitors, defending doggedly and restricting Barcelona's attacking play deep into the second half.
Messi had the best chance to open the scoring after neat interplay with Suarez but side-footed wide when well placed.
Suarez, who has endured a frustrating season so far, saw a shot blocked before his acrobatic overhead kick from the resulting corner flew wide as Ernesto Valverde's side continued to press for a late winner.
The game was largely devoid of quality, with Gerard Deulofeu, a substitute for the injury stricken Sergi Roberto, lacking any final product from the right as Messi dropped deeper in an attempt to influence proceedings.
Pitch invaders twice approached Messi in two of the match's highpoints, the forward obliging both fans before getting back to business.
Luck continued to evade Uruguay international Suarez, who struck the top of the bar with a looped shot.
Messi went close twice at the end of the match, his free-kick being saved before a clattering strike was beaten out once again by Proto.
Barcelona remain strong favourites to qualify from Group D as winners after Sporting CP held Juventus to a draw, with Barca now three points clear of Italian giants Juve with two games remaining.
Olympiakos XI: Proto, Elabdellaoui, Botia, Engels, Koutris, Romao, Figueiras, Tachtsidis, Ofoe, Carcela, Fortounis
Barcelona XI:Ter Stegen, Semedo, Mascherano, Umtiti, Alba, Busquets, Paulinho, Denis Suarez, Roberto, Messi, Suarez