BOSTON -- For the first time all season, Adam Wainwright was without his security blanket behind the plate, with battery mate Yadier Molina hitting the injured list a few hours before his start at Fenway Park. 

Despite not having his usual catcher, the Cardinals' starter looked comfortable, working into the seventh inning for the fourth straight start. But a few mistake pitches helped the Red Sox defeat St. Louis, 6-5, with the 40-year-old right-hander getting tagged with the loss, his first decision in his last four starts. 

“He’s been consistent, and he’s been going seven innings against everybody,” Red Sox manager Alex Cora said. “It’s different without Yadi behind there, looking for tendencies and certain things. Today was a lot different than what we expected, but we put some good at-bats together."

“I was disappointed in a couple of pitches,” said Wainwright. “I had command most of the time but made a couple of fastball mistakes that cost me a couple of runs there. It could have been good. I wish we could have held them there.”

The Red Sox were quick to jump on the Cardinals, with Jarren Duran stroking a leadoff triple into the center-field triangle in the first. He would come around to score on a double play to make it 1-0, but Nolan Arenado would quickly even things out in the top of the second with a blistering home run, his 12th, over the Green Monster that came off the bat at 108.6 mph, per Statcast.

Wainwright (5-5) passed Bill Sherdel for fourth on the Cardinals’ all-time innings pitched list with 2,455 career frames.

“Waino got a lot of ground balls,” Cardinals manager Oliver Marmol said. “He fell behind hitters early on but won the 1-1 pitch. A lot of 1-1 counts, 90 percent strikes, so he was able to get back into there. Overall, solid.”

Wainwright allowed just a walk in the scoreless third, but the fourth inning was where the dreaded mistake pitches began to rear their ugly heads. The Cardinals' starter pointed specifically to the pitch that Trevor Story hit for a two-run single, a 91.3 mph sinker that stayed up in the zone, putting Boston up 3-1.

Asked what he was looking to do with that specific offering, Wainwright said, “Not what I did with it. If I execute where I’m trying to, he probably doesn’t get a hit.”

He put up two more scoreless frames before the Red Sox’s bats again took advantage of mistakes and hooked him for one more run in the seventh, forcing him from the game after 6 1/3 innings of work. It was the third time Wainwright allowed four earned runs in a start this season, while his ERA jumped to 3.06.

The Cardinals trailed 6-1 with two outs in the ninth inning but would rally behind three doubles and a triple, scoring four before Paul Goldschmidt struck out to end the game with the tying run sitting at second base.

“Good rally,” said Marmol. “Guys took some pretty good at-bats, strung together some quality at-bats.”

Prior to Molina hitting the 10-day injured list, he and Wainwright were poised to move into second place all time for most starts by battery mates, but they will remain tied in second with 316 starts together for the time being. The all-time record, held by the Tigers' Mickey Lolich and Bill Freehan (1963-1975) is 324 starts together, something Wainwright is hoping will be possible before season’s end.

“I control what I can control. Yadi’s going to do the same,” Wainwright said. “If it’s possible and he’s ready to go out there, then he will.

“I knew before the trip that Yadi was going on the [injured list]. He and I talk a lot, that’s not a secret. When something happens to him, I know about it. He keeps me in the loop. I just hope he gets back soon. He’s my man. He’s my catcher.”