The New Hampshire native, who was a first-round pick of the Toronto Blue Jays way back in 1993, was just 1-7 in 2011 after dropping a 5-4 interleague decision to Kansas City on June 17.
He's since improved his slate to 8-8, winning seven of eight decisions across 11 starts, including a 5-2 win over Milwaukee on Aug. 11, in which he allowed 10 hits and two runs in eight innings.
One start since resulted in a no-decision for the 36-year-old, who gave up three runs on five hits in seven innings of St. Louis's 5-4 loss at Pittsburgh.
Carpenter is unbeaten in nine career starts against Los Angeles, going 6-0 with a stingy 1.57 earned run average across 63 innings.
The Cardinals are 7-3 in his last 10 starts.
Jon Jay went 2-for-3 with a home run for St. Louis, which had lost four of five coming in and are still 8 1/2 games behind NL Central-leading Milwaukee.
In Denver, Seth Smith's two-run home run in the seventh lifted the Colorado Rockies to a 5-3 win over the Dodgers in the finale of a three-game set.
Chad Billingsley (10-10) took the loss as he gave up five runs -- four earned -- on three hits with five walks and seven strikeouts over 7 2/3 innings of work.
For Los Angeles, rookie right-hander Nathan Eovaldi makes his fourth career start.
The 21-year-old product of Houston was a 5-3 winner at Arizona in his big- league debut on Aug. 6 after allowing two runs on four hits in five innings of a 5-3 win.
Two subsequent starts have yielded a no-decision and a loss in which Eovaldi has allowed only two more runs on seven hits in 12 innings.
Los Angeles scored just two runs in those two starts.
The Cardinals have won three of four from the Dodgers this season and have won seven of their last eight in the series.