MLB Commissioner Rob Manfred advocated for a free agent signing deadline in a radio interview Thursday, one day after Athletics slugger Brent Rooker called the idea "pretty close to the most anti-player idea you could possibly have" on social media. MLBPA executive director Tony Clark warned Manfred could be making a "self-defeating miscalculation of massive proportions."

Manfred indicated he will likely propose a signing deadline again during upcoming labor negotiations. The current collective bargaining agreement expires in December.

"I think there's going to be some more conversation about it, because I do believe that there's a marketing opportunity," Manfred told WFAN hosts Craig Carton and Chris McMonigle. "It's a great chance to kind of own some offseason weeks, which is crucial to selling tickets, selling season tickets."

Clark issued a strong statement to The Athletic defending the current system and warning against fundamental changes.

"Free agency thrives when competition thrives — on and off the field," Clark said. "If the owners are genuinely interested in improving free agency, there are many ways to get there, and we look forward to having that discussion in the coming months. But if their true interest is to blow up the very system on which our streak of uninterrupted seasons has been built — with the game reaching record heights and poised to go even higher, no less — that would be a self-defeating miscalculation of massive proportions."

Manfred dismissed player concerns that a deadline would lead to subpar contracts.

"I just — I don't put much credence in this," Manfred said. "Let's face it, on both sides of these negotiations, there's really sophisticated people who negotiate for a living all the time. You tell them whatever the hell the rules are, it's all going to turn out the same no matter what — the money's the money is the money."

Agent Scott Boras, who represents three of the biggest names still on the market including Cody Bellinger, Alex Bregman and Ranger Suarez, said Thursday he opposes a deadline.

"The sole purpose of deadlines (is to) simply restrict competition and deny players the true market," Boras said by phone. "Our current rules allow for ultimate roster construction and the best possible team for a season. Every owner wants the opportunity for time to allow him to respond to changes by his competitors. That's why there's been many significant signings more in late January, February and March, because owners have responded."

Boras said the market has been slow only for premium position players and starters, not for relief pitchers and closers.

Joel Wolfe, head of Wasserman's baseball division, has seen positive results with deadlines when clients joined MLB from abroad through the posting process for Japanese pro players.

"If there was a way to re-create the exceptional efficiency of the posting system for all the free agents, I would certainly be interested in that," said Wolfe, who represents Los Angeles Dodgers pitchers Roki Sasaki and Yoshinobu Yamamoto. "But I have yet to see a good answer as to what happens to the FA's if they go unsigned that doesn't unfairly prejudice them."

MLB proposed a deadline in negotiations that produced the current CBA and the 2017-21 CBA, as well as during 2019 talks. Manfred's goal is to keep a full 162-game schedule intact for 2027, the first season of the next collective bargaining agreement.