Slavia Prague claimed a point at Barcelona, whose coach Ernesto Valverde is likely to come under increasing fire after another poor display.
Barcelona did nothing to ease the pressure on coach Ernesto Valverde as they were held to a 0-0 Champions League draw by Slavia Prague in another uninspiring performance at Camp Nou.
Valverde saw his side stunned 3-1 by Levante in LaLiga at the weekend, and those expecting Slavia to fall victim to a Blaugrana backlash were left disappointed.
Lionel Messi had numerous chances to score and hit the frame of the goal on 35 minutes, but he was frequently frustrated by the excellent Ondrej Kolar in the Slavia goal.
His performance between the posts ensured the visitors earned a point they were good value for, having regularly found ways through the Barca defence at the other end, leaving Valverde's men with work still to do to progress from Group F, though they remain top with eight points from four games.
Barca's defence was cut open early and Marc-Andre ter Stegen was forced into action at the near post to keep out Petr Sevcik's deflected pull back.
Nelson Semedo then surged through one-on-one at the other end but was denied by smart save from Kolar, who would continue to impress.
The goalkeeper punched away a free-kick from Messi, who then left the woodwork shaking after he was left in far too much space and weaved his way in from the right, rattling the crossbar with a curling effort from the edge of the area.
Kolar thwarted Messi at the near post following fine work from Arturo Vidal, and the Slavia keeper produced an outstanding stop to prevent Gerard Pique's header from finding the net from the subsequent corner.
Jan Boril had the ball in the net for Slavia in first-half stoppage time, but he was correctly flagged for offside.
Sergi Roberto became the latest player to see an effort kept out by Kolar 10 minutes into the second half, before Messi teed up Vidal to slide into an empty net, only for the goal to be ruled as the former had strayed offside when latching on to Frenkie de Jong's pass.
Messi met teenager Ansu Fati's wonderful left-wing cross at the near post only to see his point-blank effort blocked by Kolar, whose goal was not threatened again as Slavia held firm with startling comfort.
What does it mean? More questions for Valverde
After their collapse at Levante on Saturday, Valverde would have expected an emphatic response from his side. It never arrived. Messi was unfortunate not to break the deadlock on numerous occasions, but Barca's inability to find a decisive goal and their continued issues at the back will only raise more questions for their embattled boss.
Kolar earns memorable result
Though Slavia frequently threatened on the break, they would not have earned a famous draw had Kolar not been in such stunning form, improbably coming out on top in a personal duel with Messi.
Few players shone for Barca beyond Messi, but Ousmane Dembele's performance was particularly disappointing. The forward was sloppy in possession and frequently wasted promising openings on the break.
Barca turn their attention to a league match with third-bottom Celta Vigo on Saturday. Their next assignment in the Champions League sees Borussia Dortmund visit Catalonia. Czech leaders Slavia face Teplice at the weekend, and they will seek the scalp of Inter in the Champions League later this month.