While Alcoa's on-target quarterly earnings report helped kick off a stock rally Wednesday, Shelter Harbor Capital's Brian Kelly said he saw one headwind.
"The one thing in the Alcoa report that really struck me is they talked about the trucking sector and how that was a weakness, so you have to watch that," he said. "If you want to make a bearish case at all, that's the case that you can make. But that can pick up very quickly if you get an economy that starts to pick up."
On Tuesday after the closing bell, Alcoa reported that it had met its quarterly target and raised its outlook for 2013.
On CNBC's "Fast Money," Kelly also noted one potential warning sign.
"Alcoa usually doesn't matter, and if they came out with awful earnings, it wouldn't have mattered," he said. "The only warning sign I see in today's market as we're trading now is a lot of the currencies, fixed-income markets, are not confirming this rally."
Copper, he added, was also not booming.
"I'm not saying put the bear suit on or be crazy about it, but just keep an eye on that," Kelly said.
Joe Terranova of Virtus Investment Partners said that the start of the earnings season appeared positive.
"Where are you going to get the positive contribution?" he said. "We know you're going to get it from financials. We know you're going to get it from materials. Now, if you can get it from industrials as well, that just solidifies the reason why the VIX is trading at 13. You can buy cheap protection in this marketplace, and that means the market continues to move higher."
Rosecliff Capital's Mike Murphy highlighted the low price of the volatility index.
"It tells you there's not a lot of fear in the market," he said.
"I think if you look at the marketplace right now, it's telling you you can be long your core holdings into the earnings season, and you can put on protection through the form of a put below the market. And the market right now is telling me, above this current level on the S&P, I think we're looking for 1,475."
Trader disclosure: On Jan. 9, 2013, the following stocks and commodities mentioned or intended to be mentioned on CNBC's "Fast Money" were owned by the "Fast Money" traders: Joe Terranova is long VRTS; Joe Terranova is long AAPL; Joe Terranova is long GS; Joe Terranova is long MS; Joe Terranova is long GLW; Joe Terranova is long DELL; Joe Terranova is long SWN; Joe Terranova is long XOM; Joe Terranova is long AAPL 525 JAN CALLS; Brian Kelly is long XLF; Brian Kelly is long QQQ; Brian Kelly is long XLB; Steve Weiss is long BAC; Steve Weiss is long JPM; Steve Weiss is long C; Steve Weiss is long M; Steve Weiss is long GMCR; Steve Weiss is long WLT; Mike Murphy is long AAPL; Mike Murphy is long C; Mike Murphy is long TGT; Mike Murphy is long FB; Mike Murphy is short AMZN.