Wainwright pitched 4⅓ innings, allowing seven hits and three earned runs before Giovanny Gallegos relieved him with the Cardinals trailing 3-1.
Wainwright, 5-5 with a 4.34 ERA, had minor elbow surgery after the 2017 season and was just 2-4 with a 4.46 ERA last year, appearing in only eight regular-season games.
In six seasons through 2014, Wainwright finished second or third in National League Cy Young Award voting four times.
Coming off a $97.5 million, five-year contract that paid him $19.5 million last season, the 37-year-old right-hander agreed to a $2 million, one-year contract that allows him to earn $8 million in performance bonuses as a starting pitcher, $3 million for relief appearances and $4 million more for games finished.
Information from The Associated Press was used in this report.