Bill Gross is taking over management of the Pimco Unconstrained Bond Fund, one of the firm’s most important offerings as clients pull out of its main bond funds, after its current manager Chris Dialynas leaves on a sabbatical.

The transition from Dialynas, who has been at Pacific Investment Management Co. since 1980 and has run the $28 billion Unconstrained Bond fund since 2008, to Gross is effective today, according to a regulatory filing by the Newport Beach, California-based firm. Dialynas, 59, has taken a sabbatical earlier during his career at Pimco, said Mark Porterfield, a spokesman for the firm.

Pimco Unconstrained Bond Fund attracted $10.2 billion this year through October, the most of all non-traditional fixed income funds tracked by research firm Morningstar Inc. The fund has helped the firm limit client redemptions as Gross’s Pimco Total Return, which was the world’s largest mutual fund until October, is on track to have the worst year of redemptions with an estimated $36.9 billion pulled through Nov. 30, according to Morningstar estimates. Investors are seeking non-traditional bond strategies and withdrawing money from core fixed-income funds as they anticipate a rise in interest rates.

Pimco’s Unconstrained Bond fund can invest across a broad array of fixed income, regardless of maturity, credit quality or region. Under Dialynas, the unconstrained strategy returned 5.2 percent over the past five years, behind 83 percent of peers, and fell 2.1 percent this year, behind 75 percent of similarly managed funds, according to data compiled by Bloomberg.