Manchester City manager Roberto Mancini has challenged his team to keep improving as they travel to QPR on Saturday determined to maintain their grip on the Premier League. City have been in swaggering form recently, reeling off seven straight victories in all competitions while rattling in 27 goals, a run that includes Wednesday's 3-0 Champions League demolition of Villarreal. Mancini's men are five points clear heading into the latest round of Premier League fixtures, and few would bet against them maintaining that cushion with a win at Loftus Road on Saturday. Although newly promoted QPR scored a memorable 1-0 victory over Chelsea in the west London derby a fornight ago, the limitations of Neil Warnocks's side were ruthlessly exposed by Tottenham last weekend. However, Mancini is determined not to let complacency infect his expensively assembled squad, and plans to tweak his starting line-up for the trip to London. "We want to continue to play well if it's possible, but we know that every game is hard," Mancini said. "Now we play another game in 60 hours, it will be hard and we'll need to change some players." City's position at the league summit may take the gloss off what is expected to be a celebratory atmosphere at Old Trafford, where Manchester United face Sunderland on the eve of Sir Alex Ferguson's 25th anniversary at the club. Since the 6-1 mauling by City last month -- a result Ferguson described as his "worst ever" -- United have strung together three clean sheets. Ferguson's defence will be bolstered on Saturday by the return of Nemanja Vidic, who missed Wednesday's 2-0 Champions League win over Otelul Galati through suspension, as United attempt to stay in touch with City. Sunderland manager Steve Bruce, a key member of Ferguson's first title-winning squad in 1993, meanwhile paid tribute to his former boss. "In my opinion, he’s the best there’s ever been," Bruce said. "I know you can compare him to the (Bill) Shanklys and (Brian) Cloughs, but look at what he’s done and achieved. To still be doing it after 25 years is quite unbelievable." Chelsea, meanwhile, will attempt to put their recent difficulties behind them with a trip to struggling Blackburn. An away defeat at QPR, which led to allegations of racism against Chelsea captain John Terry, was followed by last weekend's 5-3 loss at home to Arsenal. Another patchy display in Europe on Tuesday, where unheralded Belgian side Genk forced a 1-1 draw, left Andre Villas-Boas' men desperately in need of a win if they are to avoid slipping further behind league leaders City. Villas-Boas has consistently backed his under-fire captain Terry, who is set to return against Rovers at Ewood Park, despite a blunder last week that helped Arsenal take a decisive lead at Stamford Bridge. "I think John has been involved in all our Premier League games," Villas-Boas said. "He's our captain, one of the best defenders in the world, and his talent is unquestionable. So, with the talent he is, he's always up for selection." Newcastle, whose unbeaten start to the season has carried them to third in the league, are determined to preserve their fine start at Everton, with manager Alan Pardew urging his team not to look too far ahead. "I think we have an immediate goal in front of us," Pardew said. "We are playing against an Everton side on Saturday who have some good players and a manager who is one of the best in the world. "We are not really looking at the bigger picture, we are looking at the next game and if we can focus on that, we can have a really good season." Elsewhere this weekend, Arsenal entertain West Brom at the Emirates, while Liverpool face promoted Swansea at Anfield. Fixtures (1500GMT unless otherwise stated): Saturday Newcastle v Everton (1245GMT), Arsenal v West Brom, Aston Villa v Norwich, Blackburn v Chelsea, Liverpool v Swansea, Manchester Utd v Sunderland, QPR v Manchester City (1730GMT) Sunday Wolverhampton v Wigan (1330GMT), Bolton v Stoke, Fulham v Tottenham (1600GMT)