How did the seventh inning become Clayton Kershaw’s postseason blackhole?

The seventh inning again, really? Is there something mystical going on here, something that defies logic and explanation?

Clayton Kershaw pitched brilliantly throughout the uncomfortably hot night and then runs into another postseason seventh that left him a loser yet again in the playoffs.

Last season, he twice squandered leads against the Cardinals in the seventh inning. This time, the Mets score twice in the seventh, the runs the difference in New York’s ultimate 3-1 victory Friday in their National League Division Series opener.

Both times against the Cardinals, the rally started and Manager Don Mattingly stuck with Kershaw. Both times it blew up. On Friday, he took him out, it blew up.

Kershaw had walked the bases loaded with two outs Friday to bring up David Wright. Mattingly stepped out of the dugout and called for Pedro Baez.

Mattingly said going into the inning, aware of Kershaw’s pitch count (88), that they had predetermined if the lineup got around to Wright, he would make the switch. It would have been his fourth time facing Kershaw on Friday.

“David pumps on lefties pretty good,” Mattingly said. “Felt like that was going to be a spot if we got to that point, thought we were going to make a move there.”

A right-handed hitter, Wright naturally hits left-handers better. So of course he drilled a two-run single up the middle.

Last year in Game 1 against the Cardinals, Kershaw was leading 6-2 going into the seventh, and St. Louis rallied with eight runs. Five of the first six Cardinals singled in the inning. Then with two outs, Mattingly left Kershaw in, and Matt Carpenter hit a three-run double. Then he went to Baez.

In Game 4, the Dodgers were leading 2-0 heading into the seventh when the Cardinals led off with a pair of singles. Mattingly let Kershaw pitch to Matt Adams, who hit a game-winning three-run homer.

But Mattingly said none of that was on his mind when he decided to take Kershaw out this time in the seventh. It wasn’t that he had learned some lesson from postseasons past.

“No, it was more of just we felt like David’s really good,” Mattingly said. “His numbers against lefties are really good. Again, kind of getting back through [him] a fourth time.

“At that point, I got to feel like he’ll go right-handed there against David.”

In all three seventh innings, Mattingly went to Baez.

Sometimes it seems whatever a manager does works out wrong. Until one day, they hope, it doesn’t. Meanwhile, Kershaw has a postseason seventh-inning hurdle to overcome.

Follow Steve Dilbeck on Twitter @SteveDilbeck