Marlon Byrd walks around the Mets clubhouse with one of two items seemingly always in hand: a bat or an iPad. Sometimes both.

With a bat, usually splattered in pine tar, the veteran outfielder constantly takes air swings, regularly fine-tuning his stroke as he walks through the room or sits in front of his locker. With his iPad, enveloped in a grey protective case, he studies an exponentially expanding library of videos of his batting practice sessions.

It is all part of what has developed into a healthy obsession with the art of hitting since he broke into the major leagues in 2002, when camcorders and VHS tapes were his tools.

“He loves it,” Mets hitting coach Dave Hudgens said. “He’s always taking and watching his swings and talking hitting.”

Sometimes, Byrd shoots video of Mets teammates taking batting practice. From the video, which he records and can view in slow motion using an application called CoachMyVideo, he offers bits of advice. Other times, he incorporates teammates’ approaches to his.

“He’s a good guy to have, a good resource to have definitely for the team,” said catcher Anthony Recker, who recently worked with Byrd on closing his frontside while swinging.

The attention to detail has helped Byrd rejuvenate his own career this season as the second-oldest player on the Mets roster.

Last year, Byrd hit just .210 in just 47 games between the Cubs and Red Sox. He was released by the Red Sox in June and later suspended 50 games for testing positive for a banned substance.