Mark Wiedman, a senior BlackRock executive with a tenure that spans more than 20 years, is leaving the asset manager, according to a person familiar with the matter.

Wiedman, head of the global client business for the past two years, was believed to be a potential successor to Chief Executive Larry Fink.

Wiedman was instrumental in driving BlackRock’s growth in passive investing. From 2011 to 2019, he led BlackRock’s exchange-traded and index strategies while assets under management in the business increased from $500 billion to $1.7 trillion.

Wiedman joined BlackRock in 2004 to oversee the firm’s emergency assistance to governments and financial institutions during the financial crisis.

BlackRock is the world’s largest asset manager with its AUM hitting a record $11.5 trillion in the fourth quarter. The firm made two big acquisitions last year in a push to expand in private credit and alternatives. In December, the financial firm agreed to buy HPS Investment Partners for $12 billion in stock, as BlackRock looks to grow its presence in the highly popular private credit space. BlackRock also acquired Global Infrastructure Partners, an infrastructure investor, for $12.5 billion last year.