The Iceland international, 35, has been ruled out of the sold-out clash with a hamstring injury picked up in the 3-0 win over Nottingham Forest on Saturday.
Rudy Gestede, his replacement against Billy Davies' men, scored twice to secure three points which leaves City needing just a point against the Addicks to secure Premier League football. He is competing with Joe Mason for a start.
Fellow striker Fraizer Campbell (ankle) and defender Matt Connolly (groin) will not feature having both missed the Forest victory.
But manager Malky Mackay has revealed that Nicky Maynard, who made just three appearances following his move from West Ham before suffering knee ligament damage back in the autumn, is back in full training and could even make an appearance before the end of the season.
Chris Powell could name an unchanged squad when Charlton make the trip.
The Addicks hit Barnsley for six in Saturday's romp at Oakwell and Powell will be reluctant to make too many changes.
Six different scorers got in on the act, including late substitute Salim Kerkar who could be in line for a starting role after an impressive cameo.
Powell has no fresh injury or suspension worries with only Danny Hollands still out with a fractured metatarsal.
Defender Leon Cort has resumed training following a knee injury but Tuesday's game may come a little too soon as he continues to regain fitness.
Athletic are unbeaten in their last four league matches, winning three of them, and are six points adrift of the play-off places.
Source: PA
Source: PA