Arsenal boss Arsene Wenger has confirmed striker Eduardo will be sidelined for three weeks with a groin problem.
The Croatia international sustained the injury during a challenge with Manchester United defender Rio Ferdinand in the 1-0 UEFA Champions League semi-final first leg defeat.
Eduardo made his comeback from a broken fibula and dislocated ankle earlier this year but has suffered a number of niggling setbacks since the return.
French centre-back Mikael Silvestre also picked up a groin injury at Old Trafford and is expected to miss the return leg at Emirates Stadium.
Wenger said on Sky Sports News: "Eduardo has a groin problem and Silvestre as well.
"Eduardo is ruled out for three weeks. Silvestre we don't know - he will be short (for Tuesday)."
Wenger also confirmed that Dutch forward Robin van Persie will undergo a late fitness test ahead of the clash with United, while full-back Gael Clichy will be absent.
He added: "Van Persie we will assess very late, Tuesday morning or afternoon. Clichy is out."