For the first time since 1955, when they were known as the Redlegs, the Reds have two wins in their first 12 games. The 1953 Reds were also 2-10. Only the 1931 Reds, who started 1-11, fared worse.
The Reds led the Cardinals 4-3 through four innings but gave up nine runs in the next three innings.
Sal Romano, who allowed three earned runs on five hits in 4 1/3 innings, walked in the go-ahead run in the fifth. Austin Brice gave up a solo home run to Paul DeJong in the sixth.
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Reds reliever Zack Weiss made his big-league debut in the seventh and gave up home runs to the first two batters he faced, Jose Martinez and Yadier Molina, and then walked the next two batters before being replaced by another rookie, Tanner Rainey.
Rainey walked three straight batters and then gave up a sacrifice fly and later a two-run double. The Cardinals scored seven runs in the inning.
Even defense failed the Reds. They committed three errors.