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Wenger's side have fallen nine points adrift of their London rivals after a spluttering start to the season.
Arsenal have won only three of their nine league games so far and, with Chelsea unlikely to slip up against lowly QPR, they must improve that disappointing total at home to bottom of the table Burnley on Saturday.
Against that unpromising backdrop, Gunners boss Wenger acknowledges it will take a huge effort to climb to the top of the table and secure the club's first league title since 2004.
"I don't write us off, let other people do that, but Chelsea are in a strong position at the moment," Wenger said.
"I believe it would not be realistic to just think now that we'll catch Chelsea very quickly.
"We have to get consistent results to have a chance of coming back.
"I'm more focused on the quality of our games and on the consistency of our results before we think about coming back on Chelsea."
Having blown a two-goal lead to draw at CSKA Moscow in the Champions League, City fell six points behind league leaders Chelsea after losing at West Ham United and were then knocked out of the League Cup by Newcastle United.
Wednesday's 2-0 loss at home to Newcastle came despite City manager Manuel Pellegrini fielding a strong team, and goalkeeper Joe Hart has called on his team-mates to raise their game against United on Sunday.
"Not everyone's exactly at their peak at the moment, but we just need a few players, myself included, to step up," the England goalkeeper, who was rested against Newcastle, told Sky Sports News.
"It will come back. It's just one of those difficult patches that we've gone through many a time. Last season, we had less points and were in a worse position (at this stage of the season), and we won the league.
"We've got to look to things like that, but the main thing is to get it right on Sunday."
Wayne Rooney, the leading scorer in Manchester derbies with 11 goals, has completed a three-match suspension and is set to return to the United attack despite reports he has sustained a foot injury.
A 94th-minute equaliser by Robin van Persie earned Louis van Gaal's United a morale-boosting 1-1 draw at home to Chelsea last weekend.
United lost 4-1 and 3-0 to City last season, but victory at the Etihad would take them to within a point of the champions.
- No room for complacency -
After edging fourth-tier Shrewsbury Town 2-1 in the League Cup in mid-week, Chelsea host west London rivals QPR on Saturday.
Chelsea have taken 23 points from a possible 27 to date this season, but with QPR having recorded a timely 2-0 win at home to Aston Villa on Monday, centre-back Gary Cahill says his side cannot afford to be complacent.
"We have a chance to get the right result and hopefully sit back and enjoy Sunday (the Manchester derby), but it's never easy. You have to prepare right, rest up and make sure we're ready," said the England defender.
"Last season we struggled at times against teams people thought we were going to beat. It's never as easy as that."
Second-place Southampton, four points below Chelsea, visit Hull City on Saturday, having won 3-2 at Stoke City in the League Cup on Wednesday.
Southampton have belied expectations after losing a glut of key players during the close season and manager Ronald Koeman says he is not concerned about fatigue ahead of the trip to the KC Stadium.
"If you're a real football player, you'd like to play every three days," the Dutchman told a press conference on Thursday. "We need this schedule to develop ourselves."
Saturday's early game sees Newcastle host Liverpool, who remain without the injured Daniel Sturridge.
Saturday (1500 GMT unless otherwise stated):
Arsenal v Burnley, Chelsea v Queens Park Rangers, Everton v Swansea City, Hull City v Southampton, Leicester City v West Bromwich Albion, Newcastle United v Liverpool (1245 GMT), Stoke City v West Ham United
Aston Villa v Tottenham Hotspur (1600 GMT), Manchester City v Manchester United (1330 GMT)
Monday (2000 GMT):
Crystal Palace v Sunderland