Mets.com reports that prior to Friday night’s game catcher, Brian Schneider was placed on the 15-day disabled list, retroactive to Thursday, with a muscle strain in his back.

The Mets purchased the contract of catcher Omir Santos, who is expected to be arrive in time for Friday’s game and to be available if needed.

Ramon Castro is behind the plate for the Mets on Friday, starting for back-to-back games in place of Schneider.

“We are somewhat concerned,” Mets manager Jerry Manuel said of Schneider, who is batting just .143 (3-for-21).

Schneider said he has been experiencing tightness in his lower back since last week’s series in Miami. After struggling to play with the ongoing discomfort, Schneider opted to try to rest his back before it got “out of control.”

But Friday afternoon — before the club announced Schneider was going on the DL — Manuel didn’t sound quite as encouraged.

“If this thing doesn’t clear up, then we will have to make a decision based on him being available or not,” Manuel said. “Or trying to get somebody else in here to help us out.”

One person who has responded well is Castro, who hit a two-run homer in the eighth inning on Thursday night.

“I feel good at the plate,” Castro said. “I’ll do whatever it takes for the team — we’re here to win.”

Santos spent the majority of the 2008 season with Triple-A Norfolk of the International League, making his Major League debut on Sept. 5. In 11 games in the Majors, he is 1-for-11.

This will be quite a test for Ramon Castro. I’m not worried about his offense because he’s better than Schneider, or his defense which isn’t bad. I’m more concerned with Castro’s durability which has never been very good.