Tottenham Hotspur manager Mauricio Pochettino was in reflective mood after defeat in the North London derby on Saturday and highlighted Arsenalâ€™s controversial first goal as the key.
The Gunners took the lead in the 37th minute through a Shkodran Mustafi header which resulted from a free-kick awarded after Spurs defender Davinson Sanchez was adjudged to have fouled Alexis Sanchez from what looked a perfectly good tackle.
There were also hints of offside in the opener.
To add salt to the Tottenham wound, five minutes later Alexandre Lacazette got free down the right-hand side and his cross was coolly dispatched by Sanchez with what turned out to be the winner and three crucial points for the home side.
It was a day of frustration for Pochettino as he saw his Spurs team dominate possession for large chunks of the game, and though Christian Eriksen hit the post in the first half, they rarely threatened the Arsenal rearguard.
â€For me, that action (the first goal) changed the game, 1-0 down and then we conceded the second goal quickly (after that) and that was a key moment for the team,â€ the Tottenham boss said in a post-match interview with the official club website.
â€Iâ€™m disappointed because the effort was massive and we lost the game.
â€Iâ€™m happy with the performance but it wasnâ€™t enough. In this type of game, you need to have some luck sometimes to win.
â€Of course, it hurts. Everyone is disappointed in the way we lost but thatâ€™s football. We need to look forward and be ready for the next game against Dortmund in the Champions League.â€
Tottenham slip down to fourth place in the Premier League table, two points behind Chelsea, and even though they have qualified for the knockout stages in Europe, there will be a desire to bounce back with a positive result on Tuesday night in Germany.