Ken Griffin has shut down one of Citadel's stock-picking units

Citadel is shutting down one of its four stock picking units a little over a year after launching.

Ravelin Capital, a San Francisco-based unit of Ken Griffin's $24 billion hedge fund firm, is shutting down, according to people familiar with the matter. The unit struggled with underperformance, one of the people said.

Jeff Runnfeldt, who headed the unit, left on Tuesday January 31. At the time of Runnfeldt's hire, the unit set out to manage as much as $1 billion with ten teams, Bloomberg reported at the time.

Runnfeldt had previously worked at Citadel for about a decade, up until 2012, before being rehired to head Ravelin, a LinkedIn profile shows.

The unit included six teams, and the vast majority of those teams are moving to one of Citadel's other units, Global Equities, one person said.

The shutdown comes amid several other closures. Last year, Blackstone's Senfina platform closed following double-digit underperformance, less than two years after launching.