Arsenal winger Theo Walcott may need more time for him to comeback from his injury after suffering another setback in his rehabilitation, Gunners manager Arsene Wenger disclosed to ESPN FC.

Walcott is previously scheduled to suit up for the Gunners in their upcoming UEFA Champions League match with Borussia Dortmund on Tuesday night.

However, Wenger said the prolific winger may need two more weeks to recover from stomach injury.

"He had a setback," Wenger told reporters, according to ESPN FC. "He had to stop, to jog again. I don't think we will see him against Dortmund, nor Crystal Palace nor Chelsea. He is at least two weeks away now."

"You cannot rule Man United out today," he insisted. "They have big players, big experience and they are a big club. It's three games basically [to make up the gap] -- that is very quick in our league.

With this development, Walcott could sit out for the remainder of October. He's now expected to return in the Gunners' showdown with Liverpool on November 2.

Despite the absence of Walcott, Arsenal managed to stay hot this season as they have now built an eight-point advantage over the struggling English Premier League Champion Manchester United.

Still, Wenger said David Moyes' Manchester United is a team that should not be ruled out early this season.

"The eight point advantage we have starts to be a little gap but Man United are not out of the title race and we are only two points in front of all the others.

"If you have a choice nobody wants to be eight points behind. If you have the choice, you want to be in the race at the top, but it is still to early to say,"

"We've started very strongly, we're top of the league and that's where we want to stay," he told the Arsenal website. "One of the biggest things we've improved on is the start of the season.

"We've struggled in the last few years and had to play catch-up. There's an opportunity in every game to pick up points and we're just concentrating on our own games at the moment and that's proven in the start that we're having.

"Other teams have struggled so far and teams are going to take points off each other so it's important to keep focused on our own game," said Wenger