MOST READ: MasterCard, Visa Test Limits

The downturn in the economy and evidence of slowing consumer spending could put MasterCard (MA Quote) and Visa (V Quote) in the hot seat.

The financial sector has dropped to lows not seen in two decades. But the payment processing firms, each fairly new to the public markets when compared with banks and brokerages, have been labeled as two bright spots, since they have largely avoided pain from the credit crisis and housing fallout.

However, as the economy deteriorates, some observers are getting nervous. They question whether the two companies' strategy of capitalizing on consumers' increasing reliance on plastic to pay for purchases will be able to withstand the consumer troubles in the U.S. and potentially abroad.

Investors in MasterCard and Visa will be listening to hear how the firms characterize the depth of the downturn in the U.S. and will be on the watch for any forward-looking comments on their businesses, observers say. ...