The Pittsburgh Pirates‘ late summer regression appears to have begun in Colorado. The sweep by the lowly Rockies was only the third sweep of the Pirates for the season (the other two occurring to the Los Angeles Dodgers and Atlanta Braves, who lead their respective divisions).

This may be a harbinger of tougher times to come as the season winds down. We’ve seen this movie before, but the good news is that the 2013 version is likely to be much milder than what was experienced in the past two years.

In fact, the Pirates can have a losing “half-season” (after the All-Star break) and still win the National League Central.

They started with a strong first half and were 56-37 as of the All Star Break; a 34-35 finish would give the Bucs a record of 90-72, good enough to win the division based on some other assumptions listed below.

A losing second half doesn’t seem impossible when one realizes the Pirates have scored only 95 runs since the All-Star break while allowing 93. This is an extreme version of a season-long trend that has the team’s light hitting scoring only 12 percent more runs than the stellar pitching and defense give up.

If the post All-Star break trend continues for the rest of the season, the actual second-half win total could be 34, 35, 36 or some number in that neighborhood.

The low number (34) is something of a worst-case scenario, and I actually believe that Pittsburgh will finish a game or two above this level. In essence, the 90 wins I’ve hypothesized in an earlier article as the team’s 2013 ceiling is now more like its floor.

What the Pirates have done right is lead the season series against both the St. Louis Cardinals seven to three, and the Cincinnati Reds, less convincingly, seven to six. This leads me to believe that the Bucs can win six of their remaining nine games against the Redbirds and three of their remaining six games against the Redlegs.

If they actually win nine more games against the two division rivals (starting from a base of 70 going into Tuesday night’s game against the Cardinals), the Pirates would need to win only 11 games (out of 30) against the rest of baseball to bring their total to 90.

That’s a bit of a pessimistic assumption, even for me.

But based on the run differential discussed above, I’d actually be surprised if Pittsburgh wins more than 15 of these 30 games. That’s because the team typically runs “flat out” early in the season, then falls prey to the late-season wear and tear of the kind that showed up in the Colorado series.

Normally reliable Francisco Liriano was hammered in a 10-run game. A.J. Burnett fell apart for one inning, and the game. The bullpen was unable to hold the line after Jeff Locke’s six-inning, two-run quality start. Two close calls on a double play and a balk went against the Pirates. (Hopefully minor) injuries were sustained by Starling Marte and Pedro Alvarez.

In 2012, the Pirates had a lackluster August, with a record of 11-17, followed by a horrendous September-October in which they won only nine of 31 games. In 2011, the Pirates had a horrendous August with a record of 8-22, followed by a lackluster 10-18 in September.

Even if my hypothesis of a lackluster ending (11-13 wins out of a set of 30 against the non Red-bird and -leg teams) but nothing too horrendous is correct, the Pirates will make it to the postseason. Adding the further hypothesis of a strong ending against the two division rivals would mean a division title.

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