Kenley Jansen remains a concern heading into the playoffs

For eight innings Monday afternoon, the Dodgers paraded their potency. Walker Buehler, their self-assured rookie co-ace, was nearly untouchable. Their offense, packed with power, slugged a couple of home runs. They were outclassing the Colorado Rockies with a rousing display in Game 163.

Then Kenley Jansen jogged to the mound for the ninth inning with a five-run lead and exposed an unnerving reality the Dodgers must overcome to win their first World Series title in 30 years: Jansen isn’t the Jansen they rode to Game 7 of the World Series a year ago.

Nolan Arenado launched Jansen’s first pitch — a 92-mph cutter — over the left-field wall. Next came Trevor Story. He swatted the ninth pitch of…