It seems like there’s a growing sentiment among Mets fans and media that the team could and/or should non-tender Mike Pelfrey this offseason, cutting him loose instead of paying him the $5 million or so he’d likely earn for 2012.

Pelfrey is enduring a down year in 2011. Most of his peripheral stats are similar to the ones he posted in his last three seasons, but he has allowed more home runs than he usually does and his park- and league-adjusted ERA+ is at 83, well below the league average. Pelfrey yields a lot of contact so fluctuations in his performance shouldn’t surprise anyone, but his groundball rate and average fastball velocity have been on a steady decline since the 2009 season.

That is the case for non-tendering Pelfrey. That and the nagging insistence that Pelfrey’s a head case. This year people — including his pitching coach — seem to have latched on to the notion that Pelfrey withered under the pressure of being named the staff’s ace. But let’s be honest: If it wasn’t that it would’ve been something else. The pressure of being a father. The pressure of being a Scott Boras client with free agency looming a few years away. The pressure of being extremely tall.

I suspect that Pelfrey’s supposed mental issues have been overdiagnosed because a) he is among the rare, brave professional athletes willing to speak candidly about his own mental health and b) he does all sorts of strange things with his mouth and tongue and hand on the mound, which don’t actually indicate much about the man except that he has one particular nervous habit, but provide armchair body-language experts all the fodder they need to start sizing Pelfrey up for a straightjacket.

Anyway, that’s all besides the point. Whether psychology actually affects Pelfrey’s pitching more than that of his peers is immaterial: The problem if it exists doesn’t appear to be more damning or more correctable than Pelfrey’s lack of a swing-and-miss pitch, unless, I guess, Pelfrey has some mental block against learning a swing-and-miss pitch. This can go on forever.

What we know for sure about Pelfrey, on paper, is that the sum total of his last four years of service to the Mets add up a slightly below league-average innings eater. He averaged 196 innings a season from 2007-2010 and will, barring injury, reach something near that total in 2011.

If the case to non-tender him is based on the red flags presented by the declining ground-ball rate and velocity, I guess I understand it, though I’d like to see how the rest of his season plays out. If it’s based on Pelfrey’s underwhelming season or mental weakness or whatever, I don’t buy it at all.

I recognize that the dude is frustrating to watch, but I’m not sure 200 innings — even slightly below league-average ones — are something that can be easily replaced for less than $5 million dollars if there’s no obvious candidate to promote from within. If the Mets had a ton of starting-pitching depth I could understand not wanting to spend that money on Pelfrey, but none of their pitching prospects seems likely to break camp with the 2012 club.

This isn’t a decision for today, naturally, and we’ll have a clearer picture of the offseason in the offseason. But they’re going to need someone to pitch, and Pelfrey’s practically guaranteed to do that — if not particularly well, then at least frequently.