Mourinho departure cast shadow over Man U - Chelsea clash

Jose Mourinho is likely to be far from Old Trafford on Sunday but the former Chelsea manager will still cast a long shadow over his former club's showdown with Manchester United.  Mourinho's dramatic departure has hardly sunk in and already the London club have to regroup for a match they cannot afford to lose.

If Chelsea are beaten by Sir Alex Ferguson's side and Arsenal defeat Derby on Saturday, the Blues will enter the post-Mourinho era five points behind the league leaders.  A trip to the Premier League champions would be a daunting start for any new manager, but the circumstances of Mourinho's departure and Avram Grant's promotion as his successor puts the Israeli coach firmly in the spotlight.

Roman Abramovich's decision to appoint his friend has only added to the feeling that Mourinho's days were numbered from the moment Grant arrived as director of football in the close season.  So Grant has plenty to prove. The fans will wonder whether this anonymous 52-year-old has the ability to maintain Chelsea's position as one of the English's game pre-eminent forces.  But a bigger challenge could await the former Portsmouth director of football in the visitors' changing room at Old Trafford.

Several of Chelsea's players, with Didier Drogba among them, were in tears when Mourinho said his farewells at the club's training ground on Thursday morning.  Mourinho's charisma and proven track record inspired the likes of Drogba, John Terry and Frank Lampard to reach new heights and they are likely to wonder what Grant can add to their games.

If the players feel Mourinho has been harshly treated it must be questionably whether they will feel like putting their bodies on the line for Grant. Even if they do well, it will be interpreted as a salute to Mourinho rather than anything to do with Grant.

One thing is certain, Ferguson will be determined to take advantage of Chelsea's moment of weakness.  The Scot relished his duels with Mourinho, describing the Portuguese as the "new gunslinger in town", but he will be secretly delighted to see Chelsea in disarray.  Chelsea's problems run deeper than their three-match run without a win, but United's captain Ryan Giggs insists form goes out of the window in a situation like this.

"I don't think you can take form into account whenever the big teams play each other," Giggs said.  "They have a lot of special players. It has been close between us over the past few years. It always is and it will be again."

While Chelsea face an uncertain future, their London rivals Arsenal are enjoying a surprising renaissance.  Arsene Wenger's side go into the home clash against Derby top of the table for the first time since November 2004.

The Gunners have won four of their first five league matches and built on that feelgood factor by demolishing Seville in the Champions League.  After two years without silverware and the close-season departure of Thierry Henry, Arsenal were widely written off as also-rans this season.  But Wenger has infused his young side with the confidence to ignore the doom merchants and, inspired by the brilliant form of Spanish midfielder Cesc Fabregas, they are currently playing the most eye-catching football in Europe.

With everything looking so easy, Arsenal must avoid falling prey to over-confidence.

Robin van Persie is cautioning patience. "I know what this team is capable of," he said. "But I don't think we have to be the champions this year. Let's say for example within three years we have to win a few trophies. That is a better idea, a bit more realistic."