It seems that Lee is bound to lose, unless he gets a lot of reinforcements very soon or someone gets a force behind the Army of the Potomac. Rosecrans might not be a strategic or tactical genius, but he is an able organizer. With the Union army simply being larger, better trained and more completely supplied, any local victory will cost Lee's force a lot, as the battle of Strasburg did. Meaning that Lee's only options are knocking the Union armies back a bit with phyrric victories, taking losses he can't afford with strategic withdrawals or gambling everything on a single battle he cannot afford to lose, or even only take a minor victory on.