Arsène Wenger has warned his players not to rest on their laurels after two big wins inside a week.
Arsenal opened up a five-point lead at the top of the Premier League with a 2-0 victory over Liverpool at Emirates Stadium last Saturday, and became the first English team to win at Borussia Dortmund in the Champions League when they beat last season's finalists 1-0 on Wednesday.
One of the features of that midweek win was the defensive resilience of the entire team - led by centre-back pairing Per Mertesacker and Laurent Koscielny. Wenger has been impressed by Arsenal's work without the ball and he wants more of the same.
You couldn't feel in the Dortmund game that our concentration level dropped at any moment. For the first time from the first to the last minute our concentration was at a very high level
"We have made a lot of improvements at the back in our defensive game," he noted. "We have done well in the last two games, but there is a lot to do.
"We cannot come to the conclusion that we are in a position where we can relax - we have a lot more to achieve. We have won nothing at all, we have just won two games, and what is important is what we achieve in the future.
"The defensive urgency, the defensive focus of everybody from the first to the last minute [has improved]. You couldn't feel in the Dortmund game that our concentration level dropped at any moment. For the first time from the first to the last minute our concentration was at a very high level."
Mertesacker and Koscielny have developed a fine understanding at the back and Wenger believes they complement each other well.
"It does work [as a partnership], because they have the quality individually, they have the confidence and they certainly complement each other well, and also maybe because the whole team focuses to help them out as well," he said.
"We rush our game less, we do not panic, we have a bit more confidence and it is another good opportunity to show that on Sunday [at Man United].
"The confidence level is not set and certain for ever, it goes up and down with recent results of the team. Because our recent results have been stronger, the confidence levels will be higher. The commitment and the resilience need to be high as well."Copyright 2015 The Arsenal Football Club plc. Permission to use quotations from this article is granted subject to appropriate credit being given to www.arsenal.com as the source