LONDON: Chelsea's bid to reclaim the Premier League trophy from Manchester United faces its first major test this weekend as Luiz Felipe Scolari confronts the prospect of life without Didier Drogba.

The Londoners, unbeaten under Scolari, are playing the kind of attacking football owner Roman Abramovich has demanded and sit at the top of the league, but the evidence of the past two seasons suggests that losing Drogba hands their rivals a valuable edge.

The Ivory Coast striker was stretchered off with a knee injury in the goalless midweek Champion League draw with CFR Cluj in Romania, however, Chelsea said a scan showed he had not suffered significant ligament damage.

"He will not be requiring surgery," Chelsea said in a statement. "We will keep him under observation before putting an estimate on how long he'll be out, but we're certainly looking at weeks, not months."

Captain John Terry also suffered an injury in that match, and Scolari could find himself having to do without as many as eight first-team regulars for Sunday's home match against an Aston Villa side with aspirations to break into the Champions League.

With Drogba out, the pressure on Nicolas Anelka to improve his strike rate will be intensified, but Frank Lampard recognises it will take a collective effort to plug the gap left by the team's talismanic striker. "We will have to pitch in with goals from all around the team, which we can do, though the situation is not ideal," Lampard said.

"If you're a bit thin on the ground, maybe it's not so easy to rotate. Nicolas is a top-class striker, and we also have Salomon [Kalou] and young Franco di Santo. The experience is not really there, but I believe the quality is."

Drogba joins Deco, Ricardo Carvalho, Michael Essien and Joe Cole on the Stamford Bridge sidelines while Ashley Cole, Terry and Brazilian centre-back Alex are also in doubt for Sunday.

A slip-up by Chelsea could allow Liverpool to take over at the top. The Reds, who are at Manchester City on Sunday, will be hoping to reap a dividend from Robbie Keane having ended his long wait for his first goal for the club.

The Ireland captain, who scored against PSV Eindhoven in the Reds' 3-1 victory in the Champions League, said the breakthrough goal underlined the importance of his partnership with fellow striker Fernando Torres.

"I helped make two for Fernando on Saturday [in the 2-0 win over Everton] and he has responded with a great assist for me. Like any partnership, it takes time, it never always works out straight away.

"But we have been starting to link up well, and hopefully this is the beginning of a hatful of goals for the pair of us."

Like Keane, Manchester United striker Dimitar Berbatov is looking forward to the floodgates opening after he broke his duck for his new club in the 3-0 win over Denmark's Aalborg.

"It was very important for me to score, and I'm glad to have done so," the Bulgarian said after his midweek double.

Elsewhere, Sunderland are side set to feel the backlash from Arsenal's shock home defeat to Premier League newcomers Hull last weekend.

"You don't expect results like that," Sunderland goalkeeper Craig Gordon said. "You would probably expect a bit of a backlash but we're at home and we'll be ready."

Arsenal manager Arsene Wenger has admitted he felt physically sick after the Hull defeat but his recovery has been aided by a 4-0 demolition of Porto in the Champions League.

"When you go to Sunderland, you want your team to be completely at its best, and focused. I believe what happened last week will help us to do that," Wenger said.

"I believe we have a healthy attitude in the squad, and that has been shown against Porto. We want to show we have learned from the defeat against Hull."

In other matches, Newcastle will play their first match under the caretaker leadership of Joe Kinnear at Everton on Sunday, and bottom side Tottenham face Hull at White Hart Lane.