The Wall Street firm revealed on Monday that co-president Harvey Schwartz, a potential successor to Blankfein, will retire next month after 20 years.
Last week, The Wall Street Journal reported that Blankfein would most likely retire, on his own terms, ahead of Goldman Sachs' 150th anniversary in 2019, or early that year.
Goldman, memorably described as a "great vampire squid" in a 2010 Rolling Stone essay, is among the most dominant financial institutions in the world.
Schwartz will leave the bank on April 20, and Solomon will serve as the sole president and chief operating officer, the bank said in a statement Monday.
Blankfein later tweeted that the announcement wasn't his.
Schwartz's retirement eliminates a presumptive CEO candidate with a strong trading background and comes as Goldman Sachs has been trying to reinvent itself after market trends and regulations sapped profits from its once-lucrative trading business.
Schwartz and Solomon both took up level positions in the company - Co-COO - in the wake of Gary Cohn's departure to work for US President Donald Trump.
There was no specific reason in the Goldman announcement about why Schwartz chose to retire.
Blankfein and the board were impressed, insiders say, by Solomon's proven ability to build businesses at a time when the bank is looking to grow, the strength of the investment-banking team he put together, and his efforts to recruit and retain talent. Solomon, 56, a former investment banker, has been boosted by the strength in that business, where Goldman Sachs posted record revenue previous year.
Prior to joining Goldman Sachs, Solomon worked at Bear Stearns, where he helped run the now-defunct investment bank's junk bond business.
That person is David Solomon, the bank's co-president and co-COO. Before his current role, he co-headed the investment banking division and served as the global head of the financing group. Its bond-trading business, once a huge component of the firm's revenue, which hit almost US$1 billion a week in 2009, is now a shadow of its former self.
Most of the stocks on the New York Stock Exchange ended the day higher.