Centre-back James McPake is expected to miss the start of the season after suffering a suspected broken collarbone on Wednesday night as Coventry also lost their undefeated pre-season record at Dunfermline.
McPake went down awkwardly after a heavy challenge just minutes from the end of the Sky Blues' 1-0 defeat north of the border and had to be stretchered from the field.
The club are waiting for confirmation on the extent of the problem but an initial diagnosis does not look good.
Coventry went into the game without injured trio Elliott Ward, Marcus Hall and Danny Ireland while Ben Turner and David Bell did not feature due to illness.
Andy Kirk netted the only goal of the game for Athletic in the 39th minute, although on a brighter note for Chris Coleman's men, new signing Sammy Clingan made his debut for the club.
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