Mitigating Credit Risk in Corporate Bonds

John is a portfolio manager at an investment firm specializing in fixed-income securities. As part of his risk management process, he is concerned about the credit risk associated with corporate bond investments. John is aware that variations in credit ratings can impact the portfolio’s performance, particularly during periods of economic stress. To effectively manage this credit risk, he is considering implementing a specific strategy.

What is the most effective method for John to mitigate the credit risk in his corporate bond portfolio?