|| Jack Aker (14) || 12,248 || 49–86 |- style="background:#fbb" | 136 || September 11 || Mets || 2–4 || Jerry Koosman (9–11) || Steve Carlton (23–9) || Tug McGraw (23) || 10,317 || 49–87 |- style="background:#fbb" | 137 || September 12 || Mets || 3–4 || Jim McAndrew (11–5) || Ken Reynolds (2–13) || Danny Frisella (9) || 5,057 || 49–88 |- style="background:#fbb" | 138 || September 13 || Mets || 6–11 || Tug McGraw (7–5) || Dave Downs (1–1) || None || 6,185 || 49–89 |- style="background:#bfb" | 139 || September 15 || Expos || 5–3 || Steve Carlton (24–9) || Mike Torrez (16–10) || None || 20,120 || 50–89 |- style="background:#bfb" | 140 || September 16 || Expos || 3–1 || Wayne Twitchell (4–8) || Balor Moore (8–8) || Mac Scarce (3) || 6,471 || 51–89 |- style="background:#bfb" | 141 || September 17 || Expos || 3–2 || Bucky Brandon (6–6) || Mike Marshall (14–6) || None || 16,366 || 52–89 |- style="background:#fbb" | 142 || September 19 || @ Cardinals || 1–2 (10) || Bob Gibson (17–10) || Bucky Brandon (6–7) || None || 6,978 || 52–90 |- style="background:#bfb" | 143 || September 20 || @ Cardinals || 2–1 || Steve Carlton (25–9) || Rick Wise (15–16) || None || 5,569 || 53–90 |- style="background:#bfb" | 144 || September 21 || @ Cardinals || 3–1 || Wayne Twitchell (5–8) || Jim Bibby (1–1) || Mac Scarce (4) || 4,719 || 54–90 |- style="background:#bfb" | 145 || September 22 || @ Mets || 5–4 (11) || Bucky Brandon (7–7) || Tug McGraw (7–6) || None || 15,265 || 55–90 |- style="background:#fbb" | 146 || September 23 || @ Mets || 3–5 || Jon Matlack (14–9) || Jim Nash (1–8) || None || 14,465 || 55–91 |- style="background:#fbb" | 147 || September 24 || @ Mets || 1–2 || Tom Seaver (19–12) || Steve Carlton (25–10) || Tug McGraw (24) || 41,644 || 55–92 |- style="background:#fbb" | 148 || September 26 || Pirates || 1–5 || Steve Blass (19–7) || Bill Champion (4–14) || None || 8,472 || 55–93 |- style="background:#fbb" | 149 || September 27 || Pirates || 1–3 || Bruce Kison (9–7) || Ken Reynolds (2–14) || Luke Walker (2) || 5,335 || 55–94 |- style="background:#bfb" | 150 || September 28 || Pirates || 2–1 || Steve Carlton (26–10) || Bob Moose (12–10) || None ||