Watch French bonds for signs of real trouble: Trader

Europe 'papered over' its problems: Pro

The selloff in world markets Thursday because of concern over banks in Portugal is "relatively serious," said Jim Iuorio, managing director at TJM Institutional Services.

"There probably is some kind of bubble in the European [bond] peripherals, and when that bubble busts it could have a destabilizing effect," the futures and options trader told on "Squawk Box."

But Iuorio said he's not really concerned yet. "The reason I think it's only mildly serious at this point in time is because they're not selling French bonds yet. To me, that'll be the indication that thing things are really crumbling in Europe."

—By CNBC's Matthew J. Belvedere