One of Ken Griffin's senior staffers is leaving hedge fund giant Citadel

One of Ken Griffin's portfolio managers is leaving Citadel, the $26 billion hedge fund titan, according to people familiar with the matter.

Karl Kroeker, who specialized in tech, worked nearly 14 years at Citadel and left earlier in February, according to one of the people. He was a portfolio manager in Citadel's Global Equities unit in San Francisco and has not yet been replaced, the person said.

The move follows Citadel shutting its Ravelin stock-picking unit, which was also based in San Francisco, earlier this year. Some of the teams in that unit were expected to move to Global Equities.

Three units remain at Citadel: Surveyor, Global Equities and Aptigon.

Citadel, which is headquartered in Chicago and was founded by billionaire Ken Griffin, is one of the US' biggest hedge fund firms. The company managed $24 billion as of mid-year 2016, according to the Hedge Fund Intelligence Billion Dollar Club ranking. The firm now manages about $26 billion, one of the people said.

Kroeker couldn't immediately be reached for comment.