Preston Athey runs a five-star-rated fund that has handily beaten its benchmark over the past 10 years (annualized). His fund, T. Rowe Price Small-Cap Value (NASDAQMUTFUND:PRSVX), is on both Kiplinger's 25 Favorite Funds and Money's 70 Best Funds lists. And Motley Fool co-founder and CEO Tom Gardner calls Athey one of his favorite investors.

Athey, who has run Small-Cap Value since 1991 and has been with T. Rowe (NASDAQ:TROW) for more than 30 years, stopped by Fool HQ this summer as part of our speakers series. Interviewed by Fool Chief Investment Officer Andy Cross, Athey discussed his investment philosophy at great length.

Athey, a contrarian at heart, discusses the importance of diversification in the clip below (run time: 6:36).

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