Arsenal suffered another injury blow ahead of their Champions League game at Ajax Amsterdam when Brazilian midfielder Gilberto finished up on crutches after Saturday's 0-0 draw with West Ham.
Gilberto injured his ankle at Upton Park and joins Dutch forward Dennis Bergkamp as a major doubt for Tuesday's Group B game - for which Arsenal are already missing injured striker Thierry Henry and suspended forward Robin van Persie.
"He is on crutches at the moment and doesn't look good for Tuesday night," manager Arsene Wenger told reporters.
"It's bad news. With all the injuries at the moment, we just can't afford to lose Gilberto."
Gilberto's absence would be a big loss in midfield, where Spanish teenager Francesc Fabregas has been replacing Patrick Vieira and Edu, who both left the club in the close season.
Fabregas, a burgeoning talent, is likely to be partnered by the inexperienced 21-year-old Mathieu Flamini on Tuesday if Gilberto does not make a speedy recovery.
There are concerns too up front, with Henry out for six weeks and Bergkamp rated by Wenger as having only a two percent chance of beating a back and groin problem in time.
But Wenger thought attacking midfielder Robert Pires, who missed Saturday's draw with a thigh injury, had a 70 percent chance of playing in Amsterdam.
Spaniard Jose Antonio Reyes is expected to lead the attack, probably with youngster Quincy Owusu-Abeyie.
The only bright spot on the horizon is the successful return from injury of central defender Sol Campbell, who scored both goals in last Monday's 2-0 league win over Everton.
"We have done well defensively in the last two games and Sol was magnificent again today," Wenger said.
Arsenal opened their European campaign with a laboured 2-1 victory over Swiss outsiders Thun, courtesy of a stoppage-time winner from Bergkamp. Van Persie was red-carded in the game.
