Arsenal's Mesut Ozil is expected to be out for around four weeks after picking up a hamstring injury in Tuesday's defeat to Bayern Munich.
The Germany international was withdrawn at half-time in the UEFA Champions League loss at the Allianz Arena after sustaining the problem.
Manager Arsene Wenger confirmed on Friday that the club's record signing could be out for as long as six weeks - a blow to Arsenal as they challenge for the Premier League and FA Cup titles.
"Ozil will be out for three weeks," the Frenchman initially said, before adding: "When the minimum is three, the maximum is six so let's say four weeks."
Wenger continued: "It's a blow to lose Ozil but I'm confident we have the quality to deal without him. We have many good players in our squad."
January signing Kim Kallstrom could make his debut in Sunday's derby against Tottenham after overcoming a back complaint, but that game will come too soon for Aaron Ramsey, who has yet to fully recover from a thigh injury.
"(Ramsey) still has recurrent pains in his thigh, we have to be very cautious with him," explained Wenger.
"Kallstrom is back in the squad and will be available for Sunday."
Arsenal's boss also distanced himself from reports in Spain suggesting he could replace Gerardo Martino as Barcelona coach.
"My commitment is here and nowhere else," said Wenger.
|Coach: T. Sherwood|
for Sandro 68'
for N. Chadli 68'
for C. Eriksen 82'
|Lampard welcomes ´perfect´ NYCFC challenge|
|Shamrock Rovers 3 Progres Niederkorn 0: Waters at the double|
|Gerrard keen to emulate ´hero´ Beckham at Galaxy|
|UEFA Champions League Review: Red Imps make history, TNS breeze through|
|Ameobi extends Newcastle deal and heads for Cardiff|
|U.S. women celebrate World Cup victory with LA rally|
|Atletico agree Vietto deal|
|Silva appointed Olympiacos head coach|
|Presidential candidates unsure of Turan´s Barca switch|
|Toure keen to bounce back from ´disappointing´ campaign|
|El Salvador v Canada: Floro targets Gold Cup learning curve|
|Juve complete Zaza swoop|
|Costa Rica v Jamaica: Borges confident Wanchope´s men are ready|
|Marseille snare Sarr|
|Italy coach Conte to stand trial in match-fixing case|
|Castan keen to repay Roma´s faith|
|Rami thrilled to reunite with ´best coach´ Emery at Sevilla|
|Lusitans v West Ham: Tomkins seeks to silence minnows|
|Kagawa shines as Dortmund hit six in Japan|
|Alonso tips Gerrard for Galaxy glory|
|Firmino seeks self-improvement with Liverpool|
|Buffon bids farewell to Pirlo|
|Sterling named Europe´s ´most valuable´ young player|
|Casillas´ agent reveals Porto offer|
|Southampton bring in Martina|
|Dundee United accept Celtic´s Ciftci bid|
|McArthur pens new Palace deal|
|Bartomeu rules out Barca move for Pogba this year|
|Spurs have to be better now - Bentaleb|
|Milner expects central role|
|Micronesia thrashed again, this time 46-0|
|Marchisio: I cannot be Pirlo´s heir|
|Inter aiming for Champions League return - Icardi|
|UEFA Europa League Preview: Brondby and Slovan to protect handsome leads|
|Bentaleb pens new long-term deal at Tottenham|
|Barca agree Turan deal|
|FIFA bans Mayne-Nicholls|
|United States v Honduras: Klinsmann demands improvement ahead of Gold Cup opener|
|CONCACAF institutes extensive reforms in wake of FIFA corruption scandal|
|Mauri completes Milan move|
|City sign Turkey striker|
|Women´s World Cup final draws huge US TV ratings|
|My first Chelsea team better than current crop - Drogba|
|Bertrand set for lay-off after knee surgery|
|New five-year Juve deal for Marchisio|
|Allegri extends Juve contract|
|Koeman reiterates Alderweireld interest|
|Valencia bag Bakkali|
|New York City FC complete Pirlo capture|
|Panama v Haiti: Collat ready to challenge the best of CONCACAF|
|UEFA Champions League Preview: Harrison eyes TNS progression|
|FIFA sanctions Yemen for fielding ineligible player|
|Toulouse rubbish Ben Yedder exit reports|
|Mourinho ´knows what he´s doing´ with Falcao signing|
|Watford shell out club-record fee for Capoue|
|Braafheid signs Lazio extension|
|Nani finalises Fenerbahce move|
|Liverpool confirm O´Driscoll appointment|
|Liverpool have to start better - Lucas|
|USA simply too good - Sasaki|
|Portland Timbers 1 San Jose Earthquakes 0: Jewsbury wins it in stoppage time|
|No move yet for Van Persie|
|Lloyd wins Golden Ball, Silver Boot awards|
|Mascherano: I never grabbed Banega|
|Dunga requested Brazil not appeal Neymar´s suspension|
|United States 5 Japan 2: Lloyd stars with hat-trick|
|Fiorentina deny Inter criticism|
|Nani relishing Fenerbahce opportunity|