As once observed in this column, when Arsenal were gunned down at The Emirate Stadium by Chelsea, it proved that the European Champions are in a state of flux and are genuine title contenders.But the Emirates game was just one of challenging clashes played so far for Roberto Di Mateo’s team. Their next encounter is against London rivals Tottenham Hotspurs at White Hart Lane. It is another litmus test for the Italian gaffer and his rejuvenated squad.Both Manchester United’s Sir Alex Ferguson and Manchester City’s Roberto Mancini will be more eager to see the Stamford Bridge giants equally humbled. If their dream becomes a reality, then the competition takes a new shape and will turn even stiffer. Well, the Blues have such an impressive record against Spurs whether home and away. However, what makes Saturday’s clash even more important for both teams is the fact that Andre Vilas-Boas, the Spurs new boss is a former Blues manager, who was shown the exit after only 8 months in charge. And so he has an axe to grind with the megabuck owner Roman Abromovic. He wants to prove his worth as a manager and that may be he wasn’t given enough time to make his project work.Plus, so runs, however long, do end. That’s what the Portuguese proved at Old Trafford a fortnight ago. Who thought the Spurs would convincingly beat the Red Devils at OT?And the Spurs have a stronger squad than in the previous two seasons. Despite the exit of the skillful playmaker, Luka Modric, they have other enviable players in the likes of Gareth Bale, Aeron Lenon, Defoe and the new signing Mousa Dembele. But as I had opined before the game, the Spurs were very lucky to travel to Old Trafford at a time when the hosts had serious injuries in defence. That said, Chelsea have the in-form midfield at the moment and the lead striker Fernando Torres appears to have regained his form.The defence is strong as ever with Ashley Cole, John Terry, David Luiz, Ivanovic and Obi Mikel proving reliable screen, while stopper, Petr Cech is one of the best in the world. Villas-Boas knows the strength and weaknesses of their squad but most of the players he knew have since left. And he isn’t conversant with new signings.So once Chelsea wins this, they will further their credentials as favorites to win the Premier League title despite the fact that reigning champions Man City and former champions Man United will prefer to believe otherwise.But that aside, you can never count out Ferguson’s United, who has boosted his squad this season in a bid to reclaim the title. They have the best attack in the league led by last season’s two top scorers Robin Van Persie and Wayne Rooney plus Danny Welbeck and Chicharito, who can come off the bench and win a game. The loopholes are in the midfield and defence, where injuries have hit them hard! Ashley Young and Antonio Valencia have been missing for some time, while Nemanja Vidic, Chris Smalling are missing in the defence.In essence, the Red Devils are better equipped to challenge for the title than they were last season when they lost their crown on goal difference to their ‘noisy’ neighbors. So unless something extraordinarily happens in between, the clash against Potters at Old Trafford is a must win for the hosts. But Stoke has always been a funny to face for the big teams because of their direct approach and their physicality.The reigning champions, City have a harder game though. They visit West Brom on Saturday without their playmaker David Silva, who is sidelined with an injury sustained during Spain’s 1-1 draw against France.Mancini will be praying that the damage is not too serious. But Spanish international and the club’s Player of the Year — seem likely to miss at least three games.West Bromwich are stubborn customers, who have the tendency to shock the so called big four teams, especially at their place. Man City have a must win Champion League game away to Ajax Amsterdam in midweek. Nevertheless, for now till the transfer window opens in January, the title favorites remain the two Manchester clubs and Di Mateo’s Chelsea, who seem to be enjoying the lime-light once again following their heroics en-route to their first Champions League title last season.