The St. Louis Cardinals are 53-28 at the halfway point. That's the best record through 81 games since the 2006 White Sox also started 53-28 and as Jerry Crasnick writes, the amazing thing is the Cardinals have done this with projected ace Adam Wainwright making just four starts before going down with a season-ending torn Achilles.

What has fueled this first half is a remarkably deep pitching staff. Michael Wacha, Carlos Martinez and Lance Lynn have combined to go 25-10 with a 2.64 ERA, John Lackey has a 3.30 ERA, and Jaime Garcia has a 1.69 ERA in seven starts, capably filling Wainwright's slot in the rotation. The bullpen, meanwhile, has a 2.16 ERA, second best in the majors. Overall, the Cardinals have allowed 229 runs, 42 fewer runs than the No. 2 Pirates.

This hot start puts the Cardinals' staff on a historic pace for excellence, even better than the 2011 Phillies group of Roy Halladay, Cliff Lee and Cole Hamels that posted a 3.02 team ERA. The Cardinals' 2.59 ERA would be the lowest since the 1972 Orioles. Here are the lowest team ERAs since 1950:

1967 White Sox: 2.45
1968 Cardinals: 2.49
1972 Orioles: 2.54
2015 Cardinals: 2.59
1972 A's: 2.60

Those other seasons came in even lower run-scoring environments than the 2015 National League, which has averaged 4.00 runs per game. The 1967 American League averaged just 3.70 runs per game and Comiskey Park in that era was a notorious pitcher's park, as the White Sox not only kept baseballs in a room with a humidifier -- adding moisture to the balls -- but kept the grass long and wet to help their ground-ball pitching staff. In 1967, the White Sox had a 2.08 ERA at home and 2.88 on the road. The AL in 1972 was so low-scoring -- 3.42 runs per game -- that the league instituted the DH the following season. And 1968, of course, was the Year of the Pitcher. The NL averaged 3.42 runs per game and Bob Gibson pitched 20 percent of the team's innings himself, with a 1.12 ERA.

We can use ERA- from FanGraphs to account for the different run-scoring environments and the home park factor. Here are the top five figures in this category since 1950:

2015 Cardinals: 70 (100 is league average, so Cardinals are 30 percent better than average)
1993 Braves: 75
1997 Braves: 76
1954 Giants: 76
2002 Braves: 77
1954 Indians: 77

So here the Cardinals rank No. 1 with those famed Braves staffs of the 1990s and early 2000s showing up multiple times.

Can they keep it up? Well, probably not. One thing to consider is that nearly every pitcher on the staff is outperforming his FIP -- that's fielding independent pitching, which is a better predictor for how a pitcher will fare than his actual ERA. Here are some of the pitchers with their ERA and then their FIP:

Lackey: 3.30 (3.44)
Wacha: 2.66 (3.17)
Martinez: 2.70 (3.57)
Lynn: 2.53 (2.73)
Garcia: 1.69 (3.00)

Trevor Rosenthal: 0.70 (2.25)
Kevin Siegrist: 1.45 (2.68)
Seth Maness: 3.66 (2.68)
Carlos Villanueva: 1.65 (4.22)

Now, none of the starters is exceeding his FIP by a lot, but we should expect minor declines in the second half from at least some of these guys. As a team, the Cardinals have the highest left on base percentage in the majors at 81.7 percent (the Rays are second at 77.1). The highest LOB percentage since 2010 belongs to the 2011 Phillies and 2013 Reds at 77.5 percent, so you would expect some slight regression here as well.

On the other hand, the Cardinals haven't necessarily been hit lucky; their .294 BABIP allowed is just 14th in the majors, right near the MLB average of .297. They're ninth in walk rate and eighth in strikeout rate, so they're not doing anything historic in those areas. Mostly, they've limited home runs and left runners stranded.

It has been fun to watch. Martinez's growth in his first full season as a starter has been impressive, and Garcia's return from health problems has seen him pitch the best baseball of his career.

While you wouldn't expect this kind of dominance to continue, the NL does have many weak offenses this season. And, get this, of the five top run-scoring teams in the NL at this time, only 14 of the Cardinals' remaining 81 games are against those teams.

Maybe we are seeing one of the great pitching staffs of all time.