Frank Sinatra once sang of the warm September of his years. Braves hitters could sing of ice-cold Septembers in the Fredi Gonzalez years.

During Gonzalez’s four seasons as manager, neither hitting coach Larry Parrish in 2011 nor hitting coach Greg Walker and his assistant Scott Fletcher during the past three years have been able to muster even a decent offensive output from Braves hitters in the month of September.

And for the second time in that period, it’s going to cost the Braves a postseason berth this year, and likely some jobs. The hitting coaches are expected to be dismissed among other possible changes within the coaching staff and also perhaps the front office.

General manager Frank Wren is feeling plenty of heat for putting together a roster that has too many swing-and-miss hitters and not nearly enough contact hitters who get on base at a reasonable rate.

The Braves entered Sunday with the majors-worst record (4-13) in September, and the primary reason has been the offense, which went from inconsistent and pretty bad for most of the season to absolutely awful in the crucial final month.

They began Sunday ranked last in the majors this month in runs (38), batting average (.207) and slugging percentage (.281), and tied for last in on-base percentage (.266). Nine teams had a higher ERA than the Braves (4.10) in September, and all nine had better records this month than Atlanta entering Sunday.

A year ago, the Braves won the division but went into the postseason with a stagnant offense, after hitting a season-low .235 with season-low 100 runs in September. They also had a season-low 25 homers and a season-low .306 OBP in September, but finished at nearly .500 (13-14) because of their 3.31 ERA for the month.

In 2012, the Braves won the No. 1 wild-card spot despite hitting a season-low .230 in September and also posting season lows of 96 runs, 17 homers and a .305 OBP for the month. Then they went even lower in three regular-season games in October with a .215 average, no homers and .282 OBP in 93 at-bats.

They went 19-8 that September on the strength of a season-best 2.39 ERA.

And then there was the infamous collapse of 2011, when the Braves hit .235 in September with season lows of 87 runs, 22 homers, and .357 slugging for the month. Their pitching also struggled that month (4.17 ERA) as the Braves went 9-18 in September, blowing a wild-card lead that was still at 8 ½ games over St. Louis on the morning of Sept. 6.

This year, the Braves were 1 ½ games out of the second and final wild-card spot when September began. Entering Sunday, they were seven games behind Pittsburgh for the second wild-card spot, and also 3 ½ behind Milwaukee.

The Braves have only seven games remaining — four against the Pirates starting Monday at Turner Field, and a season-ending series at Philadelphia starting Friday. As recently as a week ago, it looked like the Braves-Pirates games might go a long way in determining the second wild-card team.

But that was before the Braves got swept at Texas to start a 1-7 stretch in which they scored a total of 13 runs through Saturday’s 4-2 loss to the Mets.

Freddie Freeman (.276) was the only Brave batting as high as .260 in as many as 15 at-bats in September before Sunday. Justin Upton, the team leader in home runs (27) and RBIs (97) this season, was lugging a majors-worst .125 average in September, going 7-for-56 with one homer, four walks and 26 strikeouts before Sunday.