Depends what you mean by "worry". In the sense that they are a greater risk for pulling back the folks who have fled to the Democrats and winning the election, yes, Christie and Huntsman are greater risks, but they're moderate enough that I could consider voting for them depending on the circumstances. In the sense that I'm worried about the damage they could do to the country if they win, I'm more worried about someone like Ted Cruz, who's clearly a solid politician who tends extreme Tea Party to boot, though I'd like to think that his schtick will play a lot better with Texas than the U.S. as a whole.
"Worried" from the perspective of if I was a Dem operative managing a campaign in 2016. I could easily live with Jon Huntsman as a Presidential candidate at first glance as a voter although obviously a lot would depend on positions he took during the general election campaign. Mitt Romney was a far more moderate governor than candidate for example, so you never know.