They will bounce back, it's just a matter of time.
In the meanwhile, if you've got an adequate replacement on your bench (and it sounds like you do), then plug them into your lineup until Huff and Helton start showing signs of life.
The contract year thing is a myth, but Huff should put up very good 2nd half numbers, especially if/when he gets traded.
Helton, I'm a little less sure of. He's been atrocious lately, but he's too good to be mired in this kind of slump for too much longer. Lineup protection has nothing to do with the fact that he's just not seeing the ball well. He'll come around.
Fret not, but in the meantime, I'd start Klesko and Ensberg...just don't drop Huff or Helton. Wait on them, they'll be there when all is said and done.
[size=10]"Men are apt to mistake the strength of their feeling for the strength of their argument." [/size]