Cashin, Insana watching for this sign of market bottom

Ron Insana: In corrective process
Ron Insana: In corrective process

Investors breathed a collective sigh of relief on Thursday after the S&P 500 rebounded from early lows and traded into positive territory.

Immediately, chatter surfaced suggesting the market had bottomed. Both Ron Insana and Art Cashin said in the days ahead they'll be looking for the market to retest lows.

If those lows hold, then, Insana says, pros will feel more comfortable buying.

Read More'Stunning' Fed move put bottom under S&P: Traders

Cashin agreed. "The number of stocks in the S&P trading above their 50-day got down, very close, to 10 percent. That's extreme," he said. Presumably, the extreme shouldn't last.

Cashin of UBS suggested the market may, in fact, be making a meaningful reversal. "Yesterday had all the hallmarks of forced liquidation," he said on CNBC's "Power Lunch," indicating the recent whoosh lower may have been due to the mechanics of the market more than anything else.

Read MoreUS stocks rise to session highs; energy leads gains

However, with as well as escalating and the threat of , Cashin quickly added "a positive close would be very helpful." In other words if stocks can hold their advance, negative sentiment may begin to ebb, more substantially.

Cashin also added that even if the market does close higher, "It won't clinch things. Bottoming will be a multiday process."

Insana, editor of Insana's Market Intelligence at agreed with Cashin. "I'd be careful of jumping in right here; bottoming is a process."