The rapid acquisition of mortgage servicing rights in the past year will put Walter Investment Management (WAC) and Ocwen Financial (OCN) in the top ten list of mortgage servicers by size (numbers 10 and 5, respectively), Moody's Investors Corp. (MCO) said in a report Tuesday.

But the two firms' recent acquisition of the servicing and origination platforms of Residential Capital out of bankruptcy creates ongoing credit risks at both shops due to the operational complexities for both Ocwen and Walter in merging existing platforms, Moody's wrote.

On the upside, even if the complexity of merging platforms creates credit risk, Moody's says issues related to growing pains are generally confined to servicing metrics such as delinquency rates, call center statistics, account reconciliations and investor reporting. And when the new volume is finally integrated, those metrics generally improve.

"However, given the heightened regulatory and litigation environment, residential mortgage servicers have little room for operational issues," Moody's wrote. 

Ocwen alone is pulling in a $160 billion servicing platform, which is larger than its current portfolio, Moody's said. Since Ocwen also acquired Homeward Residential, the company has essentially tripled its size.

Not everyone agrees.

Standard & Poor's said last month its "above average" residential subprime, special, and subordinate-lien rankings on Ocwen are not immediately affected by purchasing Homeward Residential.

Walter's portfolio is growing by 40% with the ResCap acquisition.

A bankruptcy court approved the two firms $3 billion bid for ResCap assets just this week.

Fitch Ratings earlier this month also said it's watching Ocwen's growth since the firm has been rapidly growing in the MSR space in the past several months.