Japanese starter Yoshinobu Yamamoto may be the most popular free agent ever — at least among big-market clubs — and that’s why execs are predicting he may cost the signing team as much as $300 million, including the posting fee.

The original estimate for Yamamoto, who’s only 25, was $200 million. But in addition to the Mets and Yankees, who both seem hopeful, the Dodgers, Giants, Cubs, Cardinals, Red Sox, Phillies, Diamondbacks and Tigers all are linked to Yamamoto.

The lobby scuttlebutt suggests the Mets and Giants have a solid chance. But the Yankees (and others) seem to have faith, too.

The Shohei Ohtani and Yamamoto derbies are holding up markets. Not their fault.

If the Cubs fall out, they could easily step up their thus far muted pursuits of Cody Bellinger, Matt Chapman and Rhys Hoskins, among others.

The mid-tier pitching market is percolating, with several teams after Sean Manaea and others.

The Red Sox were stepping up efforts to sign ex-Met Seth Lugo, who found his groove as a starter in San Diego. The Reds, Braves and Diamondbacks also are interested.