Both players have made a significant impact on this season's title race.

With Robin van Persie injured, it is hard to imagine Arsenal dragging themselves back into the championship picture without the influence of Fabregas.

And Alan Shearer is not alone in thinking Wayne Rooney is carrying Manchester United at present.

So, as he prepares for the match he describes as his side's "biggest of the season", Ferguson is acutely aware either man is capable of producing a moment of genius to win.

"The Premier League is full of great players and they are two of the best," he said.

"Fabregas has always been the important player for Arsenal and over the last few weeks, Wayne has hit great form."

Indeed, Rooney is playing so well - five goals in a week, including his injury-time winner against Manchester City on Wednesday - he is now earning comparison with the very best in the world at present.

"Sometimes players just hit consistency to a level you hope goes on for a long time," said Ferguson.

"He is in great form but it doesn't surprise me because he has always had that capability. "

Although Ferguson has no concrete answer as to why Rooney has made such significant progress recently, an answer may lie in his switch to a central striker following Cristiano Ronaldo's departure for Real Madrid.

Given his attacking prowess, it was a minor gripe that Ronaldo's inclination to defend lessened with every passing month.

But someone had to do the job and more times than not, Rooney was called upon to act as a surrogate wide-man.

Now he has no such role. And after finally taking heed of his manager and had the lesson rammed home by Fabio Capello, instead of chasing around the pitch demanding the ball like a temperamental schoolboy, the 24-year-old just sticks to the core of his job.

"Wayne thinks he could play centre-half but he is at his best when he is as high up the pitch as possible," said Ferguson.

"He has the strength and energy and courage to run in between players, get beyond players and hold players off.

"All the great strikers have needed courage."

Although United had business of their own to attend to on Wednesday as they sealed a Carling Cup final berth at the expense of City, it did not escape Ferguson's notice that Chelsea swept back to the Premier League summit with their own win over Birmingham, and still have a match in hand.

So, with the Red Devils' margin for error reducing all the time, Ferguson knows the importance of beating the only other side he believes can deprive United of a record fourth consecutive title.

"Looking at the way the league is shaping up, this game on Sunday is the biggest of the season for us," said Ferguson.

"If Chelsea win their game in hand they go four points ahead of us. That is the catch-up part.

"But Sunday's game has great relevance because both sides have a genuine chance of winning the league."

United had never won at the Emirates Stadium until last season's Champions League semi-final.

That one-sided encounter changed the run, since when Arsenal have suffered successive heavy home defeats to Chelsea, the latter occasion in November providing the trigger for a number of the Gunners' critics to write them off completely.

"It is amazing how this league has changed," said Ferguson.

"As I have said all along, the team that is most consistent will win the league now.

"Arsenal's current form has been very good. It has brought them back into the picture."