Credit Risk Mitigation Strategy

John is a portfolio manager overseeing a diversified fixed income fund. Recently, he noticed an uptick in the credit spread of one of the corporate bonds in the fund, which could indicate increased credit risk. In evaluating his options, John is considering different strategies to mitigate this credit risk. He recalls several methodologies for managing credit exposure, specifically focusing on assessing the creditworthiness of issuers and employing diversification within the bond portfolio.

Which of the following strategies would most effectively mitigate the credit risk associated with the bond that has seen an increase in credit spread?