Aaron Ramsey's return for Arsenal has been put on hold with the Welshman still not fully recovered from the thigh injury that has sidelined him since December.
With a growing injury list manager Arsene Wenger had hoped Ramsey, Arsenal's star performer earlier in the season, would be fit for Sunday's vital north London derby at Tottenham Hotspur.
"We have had to defer his comeback to full training a little so he is not available," Wenger said on Thursday.
"He is having difficulties in the final stages of his rehab. It looks to be short-term."
Record signing Mesut Ozil is also ruled out with a hamstring injury sustained in the Champions League defeat exit against Bayern Munich in midweek.
Theo Walcott and Jack Wilshere are also long-term absentees, putting a huge strain on Arsenal's resources as they try and stay in the Premier League title race.
"(Ozil) is out. I don't know for how long but it is a hamstring injury. There are scans going on," Wenger said.
By the time third-placed Arsenal face Spurs on Sunday they could find themselves 10 points behind leaders Chelsea who are in action against Aston Villa on Saturday.
(Reporting by Martyn Herman, editing by Pritha Sarkar)