So it’s no secret that the Mets will be looking for an upgrade in left field this offseason, and luckily for them, both good player Jason Bay and very good player Matt Holliday will be available on the free-agent market.

Unfortunately for the Mets, both the Red Sox and Yankees will be looking for left fielders, as well. I have no idea what specifically those clubs will look for, but Sox GM Theo Epstein has been adamant that he will try to re-sign Bay.

There’s no guarantee that will happen — it’s likely Epstein is openly praising Bay only because Bay is part of the Red Sox. But should it happen, and should the Yanks offer Holliday a blank check — also not a sure thing because of the way they spent money last offseason — it’s easy to imagine the Mets settling for current Yanks left fielder and free agent-to-be Johnny Damon.

Here’s why:

1) Durability: If you’ve followed the Mets under Omar Minaya, you recognize that their offseason tendency is always to fix the principal concern from the previous season. In 2009, that was the team’s inability to stay healthy. In 2009, Damon played in more than 140 games for the 14th consecutive season.

2) Marketability: It will be tough for the Mets to sell tickets and ads in February, but Damon would help the cause. Maybe not as much as Holliday, for sure, but Damon is a familiar face in New York with a reputation as a clubhouse leader and a hustler. The Mets could try to sell fans on his intangibles while propping him up as a “proven winner” after his contributions to the 2004 Red Sox and, should they succeed, the 2009 Yankees.

3) Illusions of power and defense: The Mets are looking to add a power bat to the lineup and upgrade their defense. Damon doesn’t really do either of those things, but he is coming off a 24-homer season and probably maintains some of his rep as a rangy defender even though he’s outgrown it. If the Mets wanted to get really creative, they could argue that Damon’s tendency to pull his homers could help him take advantage of Citi’s right-field corner.

In case you haven’t picked up on it yet, I’m not on board with this idea I created myself. Here’s why they shouldn’t:

1) He’s 35: There’s a reason very few players have played 14 straight seasons with 140 games or more. Old players get hurt more often. Signing Damon — who has managed to stay on the field despite numerous minor injuries — to a multi-year deal because of his ability to stay healthy would likely prove ironic.

2) He’s not good at defense: Damon could still boast above-average range, according to UZR, as of 2008. But in 2009, it appears the nagging injuries and Matsui-forced inability to take days off as a DH caught up with him. Also, if you’ve seen him throw, you know about his “arm.”

3) He’s the biggest sellout of all time: This is a subjective thing and I really don’t begrudge baseball players for taking the largest contracts offered to them, but leaving the Red Sox for the Yankees while shaving his caveman beard and cutting his hair was just too much. C’mon, guy. At least get yourself a beard clause in the contract. He makes Mark McGrath look like Ian MacKaye.