LONDON: In the memory of Ramires chipping the ball over Victor Valdes lies the knowledge that none of this makes much sense. The rivalry between Chelsea and Barcelona has produced a remarkable sequence of matches over the past 18 years, matches that have occasionally pushed at the parameters of what is acceptable, and frequently challenged the boundaries of what is possible. Chelsea should have no chance. Their manager is almost certainly leaving in the summer. Recent performances have been inconsistent and occasionally limp. They have lost four of their past six Premier League fixtures and have won only five of their last 16 matches in all competitions. They are fifth in the league, four points off fourth. Barcelona, meanwhile, are still unbeaten in la Liga, eight points clear of second. They have dropped only four points at home this season and won all three of their home Champions League group games. Everything says this should be a comfortable Barcelona win, and another step toward the exit for Antonio Conte. And yet the history of the fixture and the nature of the first leg offers reason for pause. Chelsea should have won at Stamford Bridge. They led 1-0 and seemed in control when a sloppy pass from Andreas Christensen, a lapse in concentration from Cesc Fabregas and a panicky lunge from Cesar Azpilicueta handed Barca an equalizer. But it was more than that. What was clear from that first leg was that this Barcelona are not the Barcelona of 2011 or even 2015. They are slower. They do not mesmerise teams with the pace of their passing. They play a more cautious game and frailties in their defending make them vulnerable, whatever results in Spain may suggest. Willian scored but he also hit the post twice in the first leg. Again and again he surged through unchallenged on the counter. The space he found should alarm the Catalans. Their switch to 4-4-2 should have added protection in front of the back four, but there was little sign of that at Stamford Bridge. Rather Sergio Busquets, the little pace he had having seemingly deserted him entirely, was overwhelmed, just as he had been in the 4-0 defeat away to Paris St.Germain at this stage last season. That tie, of course, should keep any Chelsea optimism in check — Barca have frequently redeemed a disappointing away performance in Europe with an emphatic display at home — but the lesson of that first leg was that Ernesto Valverde’s side is far from impregnable. The biggest systemic issue for Chelsea in the first leg was that by deploying Eden Hazard as a false nine they occasionally lacked an obvious outlet when they needed to relieve pressure. Although it could be argued that Hazard’s movement created space for Willian, the Belgian made clear after the defeat at Manchester City that he does not enjoy the role and, with Conte insisting he will consult players on tactics before tonight’s game, it seems likely Hazard will revert to his preferred inside-forward role with Olivier Giroud offering a more physical target at center-forward. At the end of September, Chelsea produced probably the best performance by an English side in this season’s Champions League to win at Atletico Madrid. That feels a long time ago, but if a return to Spain ignites something similar, Conte could have a glorious farewell yet.