London (AFP) - Chelsea's unexpected misstep at Sunderland has given their rivals fresh hope that the Premier League leaders might not be quite as infallible as their early-season dominance has suggested.Jose Mourinho's team remain unbeaten, but his big guns misfired in Saturday's 0-0 draw at Sunderland, allowing defending champions Manchester City to trim their lead to six points with a 3-0 success at Southampton.Mourinho named an unchanged XI for the trip to the Stadium of Light, but although they failed to break down Gus Poyet's hard-working Sunderland, centre-back Gary Cahill felt they had earned a valuable point."I think we are a different side to last year -- not just personnel, but mentally I think we are different," he told Chelsea TV."They made it a scrap, but we matched that and managed to play our football as well. When teams sit back and get back in that shape, it's very tough. We saw that last year and this was no different."But in these sorts of games, if you don't get the breakthrough, it's important we don't lose the game, and it's a point away from home."Chelsea will be without top scorer Diego Costa due to suspension on Wednesday when they host Tottenham Hotspur, who impressed on Sunday by coming from behind to win 2-1 at home to Everton.City's recent wobble appears to be behind them after they survived the dismissal of Eliaquim Mangala to see off Southampton at St Mary's.Manuel Pellegrini's side will hope to further erode Chelsea's lead when they head to Sunderland on Wednesday, but Black Cats centre-back Wes Brown has warned that, like Chelsea, the champions face a battle.Remarkably, City have lost 1-0 on their last four visits to Wearside and when asked if that sequence was likely to continue, Brown said: "After this result (against Chelsea), there's always a possibility."Every game, we go into the game looking to win it and if we show the same commitment again, I'm sure we'll have chances."Southampton will look to re-assert their top-four credentials when they visit Arsenal, who ended a two-game losing run by winning 1-0 at West Bromwich Albion on Saturday.- Liverpool, United seek momentum -Arsenal approach the encounter in sixth place in the table, in the middle of a phalanx of teams with designs on the top four.Only five points currently separate fourth-place Manchester United and 11th-place Liverpool, who claimed a first victory in five league games by edging Stoke City 1-0 at Anfield on Saturday.Brendan Rodgers's side visit bottom club Leicester City on Tuesday and under-fire goalkeeper Simon Mignolet says that his team-mates will draw great encouragement from their hard-fought win over Stoke."It is always pleasing as a goalkeeper to keep a clean sheet, but the most important thing is to get back to winning ways and hopefully we can build a bit of momentum now," said the Belgium international."There is another game on Tuesday and we will look forward to that one."United produced what manager Louis van Gaal called their "best performance of the season" on Saturday by sinking Hull City 3-0 to register a third consecutive league win for the first time in 2014.They entertain Stoke at Old Trafford on Tuesday and defender Chris Smalling, who opened the scoring against Hull, is eager to keep the ball rolling."The manager said it was our best game of the season and I think it was. It was a complete performance," said the England international."I think he said of the Arsenal result (a 2-1 win) that we ground that out without particularly playing well, but this time we did (play well)."He's said he wants six points and we want to deliver that on Tuesday against Stoke."Argentine winger Angel di Maria is unavailable for United after he succumbed to a hamstring injury against Hull, but on-loan striker Radamel Falcao is in contention to start after overcoming a calf complaint.Third-bottom Queens Park Rangers visit Swansea City, while improving Burnley, who are one place off the bottom but unbeaten in three games, host Newcastle United.Fixtures (1945 GMT unless otherwise stated)Tuesday:Burnley v Newcastle United, Crystal Palace v Aston Villa (2000 GMT), Leicester City v Liverpool, Manchester United v Stoke City, Swansea City v Queens Park Rangers, West Bromwich Albion v West Ham United (2000 GMT)Wednesday:Arsenal v Southampton, Chelsea v Tottenham Hotspur, Everton v Hull City, Sunderland v Manchester CityJoin the conversation about this story Click here to read full news..