Yesterday, in assaying the Mets’ starting rotation, I referred to the team’s offense as truly great and shouldn’t really have done so without qualification. It betrayed my aesthetic biases more than anything else.

For the spectator, the Mets’ offense was great — balanced, diverse, and capable of quick, lethal outbursts. It was a joy to watch. It also wasn’t notably better than that of a half-dozen other National League offenses. The Mets, for instance, led the league in Equivalent Average, a Baseball Prospectus statistic that expresses park-adjusted offense scaled like batting average, with a .273 mark. That was hardly great — the Yankees led baseball with a .289 mark — and not much better than the Dodgers, Braves, Phillies, Marlins, Padres, and Nationals. All those teams checked in between .269 and .272, essentially no different from the Mets. Parity (or mediocrity — you decide) expressed itself in many ways in the senior circuit this year.

This discrepancy between the facts and the impression the Mets gave that they were killing the ball this year is likely rooted in the team’s strength, a fantastic offensive sequence stretching from leadoff down through the fifth spot. From Jose Reyes to David Wright, the Mets were just devastating — even Paul Lo Duca, easily the weak link there, hit .318, and it’s hard for someone not to be fairly valuable when hitting for that high an average. And while the bottom of the order really wasn’t all that impressive, Jose Valentin’s productivity and the name value of Shawn Green and Cliff Floyd made it seem better than it actually was.

Moreover, when a team is winning and good feelings are had all around, the bad points are easily forgotten, from the inept attempts of Kaz Matsui and Lastings Milledge to hit major league pitching to Wright’s poor second half to Carlos Delgado’s long stretches of mediocre hitting. For the Mets to be as good again next year as they were this year, though, they’ll have to be cold about the situation: The offense wasn’t quite as good as it seemed. Like the rotation, competent management should keep it at the level it was at this year, but unlike the rotation, there will be a temptation to say that the lineup is fine and won’t need much upkeep — always a danger for a good team, and especially so on a team whose weakest hitters are respected veterans.

Going position by position, it’s actually a bit shocking to see how few Mets rated among the true elite. Mets first basemen, for instance, combined for an on base-plus-slugging percentage of .887 in a league where first baseman as a whole hit .879; Delgado and co. ranked 6th in the league. Mets third basemen ranked 5th in OPS. Delgado and Wright are genuinely excellent hitters, but at deep positions. Relative to the league, the Mets don’t have quite as big an advantage at the corners as you might think.

At those positions, at least, the Mets ranked in the upper tier; in left field (.737 OPS against a league average of .837) the team was next to last in the league, and at second base (remember Matsui and Anderson Hernandez?) they were third from last. Even with Lo Duca’s .318 average or not, Mets catchers were 9th in the league in OPS. This is just a thumbnail sketch — Lo Duca was clearly one of the better-hitting catchers in the league, and OPS is no final word on hitting — but there are clear opportunities for improvement.

The team’s offense was driven, far more than is generally recognized, by the league-leading production of Jose Reyes and Carlos Beltran; if the Mets can really step up the supporting cast by getting at least average production out of the outfield corners and second base, they’ll be able to better withstand potential instability in the rotation and slippage from key hitters.

That is, though, going to be a bit harder than it sounds. In the rotation, depending on what decisions the team makes, it might need anything from a legitimate ace pitcher to some batting practice types who can throw 200 innings; whatever choices are made, options are available on the free agent market. This is less so at the Mets’ positions of need. At second in particular, the choices are truly scary — the likes of Todd Walker and Jerry Hairston Jr. are among the most attractive available options, and the 36-year-old Valentin may actually be the player who makes the most sense. Because of his weaknesses (age and platoon issues), that will put pressure on the corner outfielders. There, though, Shawn Green — who is at best a mediocre player at this point in his career — is going to get a lot of playing time, and if he isn’t traded, Lastings Milledge, who isn’t ready to be a real contributor in a corner, is going to get some at-bats, too.

Short of trading or releasing Green, it’s hard to see how the Mets are going to set things up without benching an expensive veteran who expects to start or keeping Milledge either in Triple-A or on the pine, neither of which would likely be for the best for his development for various reasons.

Sportswriters are forever advocating big, ridiculous trades and free agent signings, but this is a case where the Mets probably really have to make one. They could really use a true, star-caliber hitter in one of the outfield corners or at second base to buy themselves a bit of a hedge against some bad starting pitching or a sudden decline from someone like Delgado. The problem is that the best options on the free agent market — Alfonso Soriano, Carlos Lee, and Gary Sheffield — are all bad ideas in one or another way. You don’t want to make huge commitments to veterans in their early 30s coming off career years, and Sheffield is old and dealing with wrist problems.

Were I in charge, I’d be shopping Milledge (who, leaving aside clubhouse issues, has very little chance of developing into anything more than a useful player if he’s not in center field) and one of the team’s spare right-handed relievers for a real bat, and I expect that’s what Omar Minaya will do. Do the Mets absolutely need another big stick? Perhaps not; but if you have real confidence in Valentin and Lo Duca, elderly men in baseball years, being assets at two skill positions next year, you’re a more optimistic man than I.