Gareth Bale, the Tottenham Hotspur winger, celebrates opening the scoring against Arsenal. Photograph: John Sibley/Action Images It was a breathless encounter, played at relentless pace, and when it was all done Tottenham Hotspur could reflect on moving seven points ahead of their great rivals with 10 games of the season to go. They will know from bitter experience about Arsenal's habit of overhauling them at the death but there are good reasons why Arsène Wenger's team are in this game of catch-up and this defeat, once again, provided the hard evidence. For long spells Arsenal were the better team, playing with the greater sense of order in a match of frenetic, lung-splitting pace. They subjected Spurs to some intense pressure after Per Mertesacker's header six minutes into the second half and gave everything in search of an equaliser. Yet Arsenal lost because of that bewildering little spell when they went to pieces in defence and an old deficiency was exposed that can make it feel like a trick of the mind Wenger's men began this season with three clean sheets and all that huff and puff about the impact of Steve Bould's appointment as assistant manager. What a deception it has turned out to be. Arsenal's defending has undermined them all season, just as it has ever since they used to win trophies in the past tense. It is a problem that has been neglected for far too long and in those moments, when Gareth Bale and Aaron Lennon scored within the space of two minutes, so much was revealed about the vulnerability of this team. Ultimately it boils down to the fact that Tottenham's centre-halves, Michael Dawson and Jan Vertonghen, were superb whereas Arsenal's, Mertesacker and Thomas Vermaelen defended in the important moments like two lumps of rock in a row of stalagmites. A team cannot defend this generously and hope to get away with it. For Arsenal, it can already be held up as Exhibit A why, barring a football miracle, they are going out of the Champions League. Yet it is also the first fundamental reason why they are facing the distinct possibility of finishing behind Spurs for the first time since 1995. For both Spurs goals it was one pass that dissected the entire defence, first from Gylfi Sigurdsson and then Scott Parker, but it could never have happened without the worst form of ball-watching. Vermaelen and Mertesacker ushered in Bale to put the first past Wojciech Szczesny with the outside of his left boot. Nacho Monreal was following Lennon for the second, gave up and Vermaelen again showed absolutely no anticipation. If anything, that was even more negligible than the first and Lennon made them pay, taking the ball round Szczesny's and sliding his shot into an exposed net. Szczesny had every right to come sprinting out of his penalty area to berate his team-mates. As straight lines go, Arsenal's defence was more like an infant's squiggle. Arsenal suddenly found themselves 2-0 down when they had actually looked the more dangerous side inside the opening half an hour and might have been ahead if Olivier Giroud was a more reliable striker. Mertesacker's header took a slight yet decisive deflection to give Arsenal renewed hope but their efforts, in a pulsating second half, came to nothing despite a late onslaught when their German centre-half was moved into attack and even Szczesny was pushed forward.