By FOX Sports Staff
Numerous defensive errors have cost Arsenal precious points this season; the Gunners were undone by two lapses of concentration at the back during their midweek clash with Liverpool and had to dig deep to come from two goals down to secure a valuable point with a 2-2 draw.
The draw meant that Arsene Wenger's men failed to capitalise on fourth placed Tottenham Hotspur's failure to win at struggling Norwich, and they currently remain four points behind their North London rivals.
The Gunners' defence will once again be tested when they come up against a notoriously physical Stoke side, and Mertesacker has urged his team-mates not to lose concentration throughout the game in order to ensure the victory.
"Stoke may play differently to Liverpool, but we need to be ready for it," Mertesacker told Arsenal Player.
"We must get the ball down and play our own game.
"That is very important against Stoke: to focus on our own game and cope with the long balls and the physical side of things. And then get the ball down as quickly as possible and show what we can do.
"We will try to put them under pressure so they can't play those dangerous balls into the area, and don't have a lot of set-pieces. We have to get them away from our goal and focus on what we need to do."
Mertesacker also bemoaned his side's inconsistency and warned that any lapse of concentration at this level would prove costly.
"We are not consistent over 90 minutes, we are resting too much in some parts," Mertesacker added.
"Focus is so important in football.
"You cannot switch off for five or 10 minutes because opponents are stronger than ever and the Premier League is very tough.
"When you lack a bit of focus, it is not enough."
The Gunners could only manage to battle to a 0-0 draw when both teams met at the Britannia Stadium earlier in the season.