It should work fine, but you might want to add some yeast nutrient, because there are some aspects of malt that help yeast grow and divide. Other than that, I would think that the only thing to think about is the flavor effect, which would probably be just as much as if you used it in the wort. So as long as it is not a huge starter, with lot's of corn sugar, it should be fine. So you're doin an esb. Sounds tasty Talk to ya later!
O, guid ale comes, and guid ale goes,
Guid ale gars me sell my hose,
Sell my hose, and pawn my shoon -
Guid ale keeps my heart aboon! -- Robert Burns