The Mets optioned Justin Turner to Triple-A today, thus ending — for now — the Justin Turner Lobby.

Paul DePodesta said something interesting in his Baseball Prospectus chat yesterday:

Our Opening Day roster is just that – a roster for Opening Day only. We can change it the next day and the day after and the day after. Though there’s a certain cache to the Opening Day roster, it’s really just one day in a long season. All that means is that the 2B job will probably continue to be a competition until somebody makes it their own, and I suspect somebody will.

Though I am still not convinced Brad Emaus is a better fit for the position than Turner, sending Turner down buys the Mets some time to determine if Emaus can be a long-term contributor to the team. It was the only way to keep both Emaus and Turner in the organization, so it is probably the most logical move.

If at some point it becomes clear that Emaus cannot handle the position — either offensively or defensively — the Mets can ship him back to the Blue Jays or find a spot for him on the bench and recall Turner. Going with Turner out of the gate would mean dispatching Emaus to Canada now.

If Emaus is going to start the bulk of games at second base, as most suspect, Daniel Murphy becomes the team’s primary left-handed bat off the bench. And that brings up a point I made to Matt Cerrone yesterday: Willie Harris becomes somewhat redundant on the roster.

Terry Collins has raved about Harris’ versatility, but Collins raves about practically everyone. It’s hard to envision a situation calling for a left-handed bat in which the team would choose Harris over Murphy (bunting?), and Scott Hairston gives the Mets a suitable fourth outfielder with plenty of experience (more than Harris) in center field. Harris can back up the infield positions too, but presumably the first call for all replacement-infielder needs will go to Chin-Lung Hu.

Most of the media has acted all spring as if Harris is a lock for the roster. Harris has an opt-out in his contract, so though he was signed to a Minor League deal he cannot be forced to accept an assignment to Buffalo. Internet legend Nick Evans, out of options, would have to pass through waivers to be sent to Triple-A.

If Carlos Beltran needs a week or two on the Disabled List to start the season, it buys the team some time to make a decision — the Mets could keep both Harris and Evans around, since presumably Hairston would be the stopgap in right field.

But if Beltran is ready to go by April 1, it seems to me (and I’ve said this before) like the team might be better served keeping Evans over Harris. Though Evans cannot boast quite the same defensive versatility or Major League resume as the veteran, he is seven years younger, locked up under team control for way longer and has more offensive upside.

I realize I’m once again quibbling over the 25th spot on the roster and that this season, it seems like the Mets’ front office might actually be thinking about these decisions more than I am. Perhaps they think Harris is the sparkplug that will catapult the Mets to contention, and Evans is doomed to a Hessmanian life of itinerant Triple-A mashing. But since neither is obvious, I’d rather see them go with the younger player and try to convince Harris to accept the Minor League assignment, knowing that he’ll likely get the first call when someone inevitably goes down with injury.

Isringhausen played catch on flat ground Tuesday and pronounced himself fit after taking what he said was “4-5 days off” because of inflammation in his elbow. The Mets had indicated Monday that Isringhausen was shut down for one day, but the pitcher said he took off more time, and his elbow was helped by taking anti-inflammatory medicine.

Isringhausen said he will throw a bullpen session Wednesday, have a day off and then resume pitching every other day as he tries to make the team as a reliever. Manager Terry Collins said he hoped to get Isringhausen into a game Wednesday, but then said he would discuss the pitcher’s schedule with Warthen.

– Anthony McCarron, N.Y. Daily News.

Look: I want Jason Isringhausen to make the Mets’ Opening Day roster. Isringhausen, with all the hope and hype surrounding him, played a vital role in the summer of 1995, one of my favorite years of Mets fandom. His return to the team would make for a great story, plus he has been an excellent reliever for much of his career. If he could pull it all together for one more season, he would be a very valuable cog in the Mets’ bullpen.

But the thing about Izzy, heck, the thing about most 38-year-old pitchers — not just the ones with Izzy’s lengthy medical history who haven’t thrown more than eight Major League innings during the Obama administration —  is there’s a pretty good chance he falls victim to injury at any time. This four-to-five day shutdown is not a big deal in Spring Training because Grapefruit League games are meaningless. But how often will Isringhausen need to be shut down for four to five days during the regular season?

Who knows? He says he feels good, apparently. We will know more after he throws a bullpen session today.

If Isringhausen makes the Major League roster, it will come at the expense of one of Pedro Beato, Manny Acosta and Pat Misch. Beato is a Rule 5 pick who would have to be returned to the Orioles, Acosta and Misch are out of options and would have to clear waivers to be sent to Triple-A. Though none of those relievers has anything like Izzy’s resume, they’re all more likely than Isringhausen to stay healthy for a full season, or, for that matter, a full month.

The Mets’ front office is, presumably, working with more information than I am. They should have a better sense of the severity of Isringhausen’s elbow inflammation, the potential of Beato, Acosta and Misch to help the club over a full season, and the chances that Acosta and Misch would clear waivers.

I guess the question is: Is Isringhausen, at 38 and basically four seasons removed from being an effective Major League reliever, going to hold up long enough and be so much better than Acosta (or pick any of the three) that it’s worth losing Acosta?

Maybe. Acosta and Misch are known quantities, and neither is likely to go all Cliff Lee on the National League in 2011. But they’re both decent enough to contribute to a big-league bullpen, and if Isringhausen’s not healthy he won’t be.