Why I left Pimco: Mohamed El-Erian

Mohamed El-Erian, former Pimco CEO and one-time heir apparent, told CNBC Monday that he left the investment giant because he wanted to do something different.

While refusing to comment directly on his reportedly rocky relationship with Pimco founder Bill Gross, El-Erian said he has nothing but admiration for his former partner.

El-Erian described his departure as a "difficult personal decision," in an interview on " Squawk Box ." El-Erian said Pimco has a great bench and won't miss him too much. He also called Gross one of the world's best investors.

Earlier this year, El-Erian abruptly left the investment giant in the wake of differences with Gross, who publicly let his displeasure with the resignation be known.

Read More Damage control at Pimco after Gross, El-Erian clash

El-Erian, who said he also wanted more family time, has stayed on with Pimco's parent company, German insurer Allianz, as chief economic adviser and he attends meetings of the international executive committee. He's also working on a book.

Gross is dealing with weak performance and massive outflows in several marquee funds at Pimco, which has $2 trillion in assets under management.

The flagship $232 billion Total Return bond fund, managed by Gross, has seen $51.62 billion of net outflows in the 12 months ending March 31, or 18 percent of beginning period assets under management.

El-Erian stood by his assertion that Gross is a great investor-by asking the question: "Do you know any long term investor who hasn't had a rough time?"

-By CNBC's Matthew J. Belvedere. Reuters contributed to this report.

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