All too often, claims are made that one or another series will have a playoff atmosphere, or will show what a team is made of, or will show whether that team can win when it counts.

These claims are usually rubbish. If someone decides they want to measure the Mets by this week’s set with the San Diego Padres, though, one can only object so much.

What makes this series special is that the Padres’ Chris Young and Jake Peavy, who are first and second in the National League in earned run average, will both be pitching at Shea. Between them, the two have thrown 295.3 innings this year, with a 2.07 ERA. This makes one think that the Padres — two-time defending division champions and current leaders in the wild-card race — stand an excellent chance of making the playoffs, and of winning the pennant if they do. A series win by the Mets, or even an especially well-played series, would show them off as one of the league’s great powers, while a loss would confirm the nagging feelings of most observers that the Mets, no matter their winloss record, aren’t quite as right as they could be.

Few teammates have ever pitched as well as Young and Peavy are pitching right now. Young’s 1.93 ERA is impressive enough, but more so in context. ERA+ is a measure that adjusts ERA for park effects and league scoring levels, and indexes it on a scale where 100 is average (the statistic is available at baseball-reference.com). Young’s ERA+ is 213. Since 1947, six pitchers have recorded a better mark: Pedro Martinez, who did it three times; Greg Maddux and Roger Clemens, who each did it twice, and Bob Gibson, Dwight Gooden, and Kevin Brown, who each did it once. Peavy’s own ERA+ is 188, bettered over the last 60 years by just 14 men. The only team in recent memory to get comparable performances from two top starters — the 2005 Houston Astros, whose rotation was anchored by Clemens and Andy Pettitte — won the National League pennant.

The two make an odd pair. Peavy, who led the league in ERA in 2004, is (perhaps generously) listed at 6 feet 1 inch and 180 pounds, while Young is listed at 6 feet 10 inches and 260 pounds. Peavy is, despite his frame, a traditional power pitcher, who throws a very hard fastball and a lively slider. Young rarely breaks 90 with his fastball, and hardly throws any other pitches. What they have in common, aside from their excellence, is that they’re fly ball pitchers who almost never allow home runs.

Four pitchers in the league, per data available at hardballtimes.com, allow less than 6% of the fly balls they surrender to go over the fence. Two of them are Young (2.7%) and Peavy (4.2%). For a point of relative comparison, John Maine — much of whose success is a result of his ability to keep his fly balls in the yard — clocks in at 10.8%.

Much of this, of course, is because of San Diego’s Petco Park. Because of its large outfield dimensions and the region’s heavy air, the park cuts home runs by about 25% as compared to an average one in a typical year. Neither man, though, is an illusion: While Young’s home ERA is a preposterous 0.66, his 3.30 road mark would be good for eighth in the league, while Peavy’s road ERA is 1.06. The two will pose as tough a test for the Mets as any on offer in the game right now.

So, if one is inclined to look at this series as a benchmark for the Mets, what to look for? Inside baseball. It’s a truism that against really good pitchers, all teams have to work the count, take extra bases, advance runners, and so forth. But Young and Peavy are brutally difficult pitchers to hit for any power, and they’re liable to be especially so at Shea, which is no Petco Park, but is of generous enough dimensions. Despite widespread complaints about their lack of power as compared to last year, the Mets, who are fifth in the league in home runs, are actually fairly reliant on the home run. This series will probably see them rely on pitching, defense, sound place hitting, and the ridiculous baserunning of the top half of the lineup. It will be a good opportunity to see how reliable those might be against top competition. I somehow doubt that we’ll be able to tell what the Mets are made of or whether their wills are built of iron or other metals based just on three games — but for once, we may be getting the vaunted October preview in August. It’s good enough for dog days.

tmarchman@nysun.com