Arsenal FC defender Sol Campbell will miss the start of the season, while two others are rated doubtful.
"Campbell is definitely out, Patrick has the best chance of playing but Thierry is a big doubt," said Wenger, who led the north London club to the English title last season. Henry and Campbell both have achilles problems while Vieira has a thigh injury.
Arsenal open their league campaign with a trip to Everton FC on Sunday 15 August. They will begin their 2004/05 UEFA Champions League challenge in the group stage.