Add one more potential starting pitching arm to the free-agent market.

A few teams are inquiring about Clay Holmes transitioning from the bullpen to the rotation, including the Mets, a source told The Post.

Holmes has not started since 2018, his debut season with the Pirates. But he was a starter throughout his minor league tenure.

Teams are more aggressively looking at relievers returning to the rotation due to recent success in that area. Kansas City’s Seth Lugo just finished third for the AL Cy Young.

San Diego’s Michael King finished seventh for the NL Cy Young and Reynaldo Lopez finished 11th. Zack Littell has enjoyed rotation success since the Rays converted him back to a starter in 2023.

Last offseason in free agency, the Giants signed Jordan Hicks to a four-year, $44 million contract to transition to the rotation and the Braves inked Lopez for three years at $30 million and King was a key element in the Yankees’ trade for Juan Soto.

Lugo, after a good transition to starting in 2023 for the Padres, signed a three-year, $45 million pact with the Royals.

Multiple teams also are looking into turning free agent Jeff Hoffman back into a starter after he made the All-Star team as a Phillies reliever in 2024.

Holmes also was an All-Star this year, for the second time as a reliever.

What teams see in Holmes to potentially move him to the rotation is the ability to throw two fastballs (four-seamer and sinker), two breaking balls (slider and sweeper) and the aptitude to develop a changeup. The sinker is viewed as a dominant pitch.

Plus, Holmes has a track record of durability as a reliever. The righty has appeared in the eighth-most games in the majors the past four seasons combined plus another 19 postseason games, including relieving in 13 of the Yankees’ 14 postseason games in 2024.

The Mets appear to be staying out of the high-end rotation market currently headed by Corbin Burnes and Max Fried and trying to replicate the success they had on shorter deals last year with Sean Manaea and Luis Severino.

To that end, they have an agreement for two years at $34 million with Frankie Montas. Holmes would fall into this realm of requiring just a two- or three-year deal.

For the Mets, Holmes could try to follow in the path of King, a former Yankee teammate, and provide a rotation answer for the Mets.

And, if that failed, the Mets need relievers, notably someone who could be setup to and safety net for Edwin Diaz. Because Holmes can do that from the pen, he has a strong market.

Holmes, who turns 32 in March, led the majors in blown saves (13) in 2024 and lost his closer job with the Yankees. But his overall body of work since being traded from the Pirates was outstanding and that includes a 1.35 ERA in those 19 postseason games, including 17 in which he was unscored upon.