U.S. Secretary of Labor Marty Walsh is leaving the Biden administration, according to people familiar with the matter.

He has been offered the job as executive director of the NHL Players’ Association, which represents professional hockey players in Canada and the U.S. Walsh is the first member of President Joe Biden’s Cabinet to step down.

The news was first reported by Daily Faceoff.

His exit will cost Biden not only a major ally to organized labor, but one of his top campaigners. In 2022 alone, Walsh traveled to 39 states to meet with workers and talk about the Biden administration’s agenda.

The departure also leaves the agency without a permanent confirmed chief amid a contentious contract fight at West Coast ports that threatens to clog up U.S. supply chains.

The agency’s day-to-day policy work is expected to continue uninterrupted as Walsh vacates his office at the Frances Perkins Building. Deputy Secretary Julie Su is expected to become acting head of the agency, as set out under the Federal Vacancies Reform Act and is likely already familiar with most of the staff within the Office of the Secretary.

It’s unclear who would be an obvious replacement for Walsh.

Biden could face pushback if Su were to lead DOL for too long, as many business lobbyists have raised concern that she could take the department in a more liberal direction based off of her work as California labor secretary.

During his nearly two-year tenure as head of the U.S. Labor Department, Walsh drew both scrutiny and praise for his outspoken support of labor unions, notably joining striking Kelloggs workers on the picket line in Pennsylvania in 2021. Walsh was also a key player in negotiations between unions and freight companies that sought to avoid a rail strike that would have disrupted the national supply chain.

At least one Republican was critical of Walsh’s coziness with unions upon learning the news.

“Secretary Walsh’s job performance doesn’t warrant celebration, it warrants the penalty box—at best,” Rep. Virginia Foxx (R-N.C.), the leader of the House committee that oversees DOL, said in a statement. “At every opportunity—he has failed to be a balanced and neutral actor in his role, selling out the American worker for Big Labor. America’s workforce deserves better.”

One worker advocacy group praised Walsh’s work in reaction to the news, and called on Biden to quickly name a replacement who will continue the administration’s focus on expanding workers’ rights.

“We hope the next Labor Secretary builds on Mr. Walsh’s successes in supporting the collective power of workers, particularly immigrant workers,” Nadia Marin-Molina, co-executive director of the National Day Laborer Organizing Network, said in a statement. “Valuing immigrant workers’ contributions, bringing immigrants into the social contract, removing chronic injustices from the labor and immigration systems—these are vitally important goals. We urge the President to quickly name a successor who will pursue them.”

This isn’t Walsh’s first foray into sports politics. In 2022, he offered to help end the lockout between Major League Baseball and its players’ union.

Known for the ability to bring both labor and management to the table in his previous role as mayor of Boston, Walsh continued that approach in his leadership at the DOL, often drawing plaudits from management-side groups for his openness.

Walsh was confirmed as the head of the DOL in March 2021, and led the agency as it attempted to require COVID-19 vaccines at workplaces and update rules on whether workers should be considered independent contractors or employees under federal wage law.

Walsh also oversaw the creation of the office of unemployment insurance modernization at the DOL, which sought to address the failing technology that led to millions of dollars lost to fraud and massive delays during the pandemic.

The former head of the Boston Building and Construction Trades Council also co-led a White House taskforce on Worker Organizing and Empowerment, which outlined steps the federal government could take to encourage collective bargaining within the federal workforce and in federal contracts.