Ken Griffin's $26 billion firm has made a hire from a struggling hedge fund

A struggling hedge fund has lost a portfolio manager to Ken Griffin's $26 billion Citadel.

The portfolio manager, Jennifer Pollak, is moving from Folger Hill Asset Management to a Citadel stock-picking unit, Aptigon. Citadel confirmed the hire.

Folger Hill, founded by ex-SAC Capital chief operating officer Sol Kumin, was down about 15% last year through November in its main fund, and earlier in 2016 lost about a third of its assets, Reuters reported.

The firm managed about $1 billion as of mid-2016, according to the Hedge Fund Intelligence Billion Dollar Club, and assets fell to about $600 million just three months later, according to Reuters. The firm now manages more than $1 billion, according to a person familiar with the matter.

Pollak is the first portfolio manager to voluntarily leave the firm, according to a separate person familiar with the matter.

Last year, Citadel's Aptigon unit poached about 17 portfolio managers from Visium Asset Management amid an insider-trading scandal, imperiling a potential sale to another asset manager.