DORTMUND, Germany — The trouble is that the solution is indistinguishable from the problem. That is the trap that Barcelona cannot quite escape, the Gordian knot that has tangled and ensnared the club, and tightens with every day and every game that it is not unraveled.

There is nothing intrinsically wrong with leaving Borussia Dortmund with a clean sheet and a precious point, even for a team with Barcelona’s standards and scale. Its scoreless draw Tuesday is not a bad result in any context; given this club’s recent memories of road trips in this competition, it could easily be seen as a sign of progress.

Barcelona is, after all, still haunted by what happened at the Stadio Olimpico in Rome in the spring of 2018. The specter of Anfield, just a few months ago, remains seared onto its collective mind. Last year, in the traditional eve-of-season speech the club’s captain gives at Camp Nou, Lionel Messi could only promise to make amends for the former; this time, months after the collapse at Liverpool, he admitted it was “hard to say anything” at all.