Arsenal manager Arsene Wenger lamented missed chances as his team failed to take advantage of Leicester City and Tottenham Hotspur slipping up.
The Gunners lost 2-1 at home to struggling Swansea City, and saw Petr Cech and Laurent Koscielny injured on a disastrous night.
The result means that Arsenal have now lost three games in a row, including two in the last four days, and have just four wins in their last 12 overall.
A win would have seen them go level on points with north London rivals Tottenham, whom they face on Saturday afternoon, but instead they remain three points away.
"We created many chances and were unlucky in our finishing. It was a very disappointing result," Wenger said after the loss.
"I'm worried about results. It's a very difficult moment for the team so we need to focus on ourselves and do the basics.
"Cech got a muscular problem at the end of the game. He will not play on Saturday. I have full faith in [David] Ospina."
Wenger added how he rued missed chances.
"We hit the bar a few times, we were on top, we were unlucky. To lose a game like that is a shame but we have to respond.
"I still can't understand that because it's just under the eyes of the referee and we were unlucky with that decision.
"At the moment we lack a little bit confidence in front of goal. We have to deal with that."