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WaMu, which bought the subprime card company Providian in 2005, said it expects card charge-offs this year to rise to 10.5% of receivables, from 6.5% in 2007.

Citi's "managed" net credit loss ratio jumped 202 basis points -- just over two percentage points -- to 6.53% in the quarter.

Higher credit costs reflected "the housing market downturn, higher fuel costs, rising unemployment trends and higher bankruptcy filings, as well as the continued acceleration in the rate at which delinquent customers advanced to write-off," it said on July 18.

To be sure, Visa is still consolidating its global businesses in the wake of a restructuring it completed in order to prepare for its March IPO.

"As they standardize all their fee income structures, you could actually see an enhancement to the revenue yield," Sakhrani says. For MasterCard, "it's about maybe not reinvesting as much" by temporarily pulling back on certain growth initiatives, he adds.

Visa and MasterCard have each acknowledged the slowdown in consumer spending in the U.S. this year, but neither seems deterred regarding their growth forecasts as they look to expand globally with various products.

"There are more opportunities for us than threats," MasterCard CEO Robert Selander said in late May.