Arsenal defender Per Mertesacker admits their title credentials will be tested in the coming weeks.
Arsenal will look to maintain their five-point lead at the top of the Premier League in matches against Manchester City and Chelsea prior to Christmas.
"It is always difficult especially now after 15 games in the league, the Christmas period is coming, you think you have a good chance to achieve something this season but you have to keep your momentum and that is really important," said Mertesacker.
"Now everybody is pulling a bit, questioning our group and if we can maintain that level so we have to stay together and think that ' yes, we are strong enough'."
