Kenley Jansen and Dodgers are burned by Melvin Upton’s ninth-inning homer

The last pillar of the Dodgers bullpen, the lone reliable man in this tinderbox assembled by the team’s president of baseball operations, Andrew Friedman, crumbled at 11:07 p.m. on Friday. That was the moment Kenley Jensen yielded a walk-off, two-run home run to Padres outfielder Melvin Upton, Jr., to usher the Dodgers toward a stunning, 7-6 defeat.

Manager Dave Roberts had called upon Jansen to collect a four-out save, a common task for him during this season. Jansen handled the first out with ease. But after a bloop single to open the ninth, Upton walloped a 92-mph cutter for Jansen’s first blown save of the season.

The loss felt crushing after the roller-coaster events of the evening. Justin Turner had resuscitated the team with a two-run homer in the eighth. Roberts asked Jansen to hold the line. Jansen, like so many of his brethren this season, could not handle the assignment.

Inside his office, as dejected players filtered out of the clubhouse, Roberts sought to cast this stretch of torture as a hero’s trial.

“Sometimes you get snake-bit, and you’ve got to ride it out,” Roberts said. “And it tests your character, and how much our team can stay together. For us, the coaches, the 25 players, we’re not going to waver. We’re going to keep going. And I think we’ll be better for it.”

The Dodgers front office chose Roberts to manage this club last winter, in part, because he projected relentless optimism. What the front office did not provide him with, at least for these first two months of the season, is a bullpen capable of handling major-league competition.

To see Jansen stumble is not an unfathomable event. Even Jansen, one of the best closers in baseball and a man without a blown save since last August, must be considered fallible. But the inconsistency of the other relievers has increased his importance. He operates under the same rules that apply to Clayton Kershaw: The Dodgers cannot afford to lose when Jansen enters a save situation.

“It’s a tough one,” Roberts said, opting for an understatement over abject despair.

So the team lost on Friday, and continued an alarming trend. The Dodgers embarrassed the Padres during the first weekend of the season here, outscoring their hosts, 25-0. The subsequent weeks showed the gap between the clubs was not that wide. Both teams have gone 18-22 since.

Scott Kazmir threw six scoreless innings here during that joyful opening weekend. On Friday he walked seven, gave up five runs and exited in the sixth inning with two outs, failing to build upon an encouraging outing against St. Louis last week.

Facing a much less potent offense, Kazmir appeared either unwilling or unable to locate pitches. In 5 2/3 innings, Kazmir walked nearly twice as many batters as Kershaw has (four) in 70 innings.

“It’s almost embarrassing,” Kazmir said. “Seven walks. It’s unacceptable.”

He looked stricken after a pinch-hit, two-run homer by Padres catcher Christian Bethancourt gave San Diego the lead in the sixth. In the aftermath, catcher A.J. Ellis blamed himself for feeding Bethancourt a cutter on the inner half of the plate.

“There were some pitches we’d like to take back, a lot of regrettable pitch calls that I made,” Ellis said. “I take responsibility for a lot of the runs that were put out there today.”

It was a night for regret. And the most dispiriting aspect of the loss was how close the Dodgers were to one of the more uplifting victories of the season. Trailing by a run in the top of the eighth, Carl Crawford came off the bench to record a two-out single. Up came Turner.

The Dodgers offense had lain dormant since Yasiel Puig launched a two-run home run off reliever Carlos Villanueva in the fifth. Now Turner faced right-hander Brandon Maurer. He hammered a 2-0 fastball into the right-field corner, where the baseball just cleared the fence. Turner sprinted around the bases and chest-bumped Roberts in the dugout.

“That homer right there was one of the highest points we’ve seen in awhile,” Roberts said. “Under the circumstances, where we’re at offensively as a club, to get that big hit, that big lift, we were all excited about it.”

The happiness did not last -- but the growing discontent with the direction of this club will. The ongoing travails of the pitching staff placed added interest on the minor leagues. In Rancho Cucamonga, Hyun-Jin Ryu gave up a pair of home runs to Class-A hitters, but still completed three innings. It was his second rehabilitation start as he returns from shoulder surgery. He could be ready by late June.

A far more intriguing outing occurred in Oklahoma City. Julio Urias lengthened his streak of scoreless triple-A innings to 27. He struck out five batters and yielded three hits. Every five days, Urias lowers his earned-run average and heightens expectations for his eventual major-league debut -- whenever his employers deem the situation right.

The team’s continuous caution with Urias may be approaching a point of diminishing returns. The big-league pitching staff aches for sustenance, with both the rotation and the bullpen dragging in recent days.

Kazmir dumped his club into a two-run hole in the second inning Friday. He dug the ditch with his own hands. Kazmir issued a one-out walk to third baseman Brett Wallace, a .213 hitter on the season, and hit Alexei Ramirez, a shortstop with a .268 on-base percentage, with a cutter.

A passed ball by Ellis moved both runners into scoring position. So after Kazmir struck out outfielder Jose Pirela, Roberts ordered an intentional walk to load the bases for rookie pitcher Christian Friedrich.

Kazmir buried Friedrich into an 0-2 count, but could not put him away. Relying solely on his fastball, Kazmir let the count draw even. On the seventh pitch of the at-bat, he pumped a 91-mph fastball down the middle. Friedrich cracked it into center field for a two-run single.

“That’s something that was a nightmare,” Kazmir said. “To feel so good, and next thing you know, a couple walks, a hit batter, a hit up the middle by a pitcher -- it’s frustrating.”

The Dodgers cut into the deficit in the third with an RBI double by Corey Seager. Puig singled to lead off the fourth and scored on a double by Yasmani Grandal.

Puig returned to the plate in the fifth. After a single by Trayce Thompson, he ignored a pair of outside fastballs from Villanueva. He did not ignore a lifeless changeup. Puig kept his balance as the baseball traveled deep into the zone and lifted an opposite-field shot, his seventh homer of the season.

The two-run lead did not last long. Kazmir surrendered a homer to catcher Derek Norris to start the bottom of the inning. Bethancourt took him deep an inning later. The seesaw swung back into the Dodgers’ favor with Turner’s home run.

After recording the last out in the eighth, Jansen wore a hoodie inside the dugout to ward off the chill. He could not hold off the Padres. First, there was bad luck. With the outfield pushed toward the walls to prevent doubles, first baseman Wil Myers dunked a single into shallow center field. Then Upton hammered an 0-2 cutter at the belt.

Jansen stomped off the field. He exited the clubhouse as reporters were still waiting to be allowed inside. He left the ballpark and walked into the cool evening, a victim of both the Padres and of circumstance.

When the Dodgers crafted this roster, the buzzword was depth. Yet the first two months of the season rejected that premise. The team does not rely on depth. It relies upon star power, upon the backs of men like Kershaw and Jansen. When one of those men falter, the ripples run deep.

“When you get hit, you need to fight back,” Roberts said. “I think our guys are going to fight back. No one’s going to feel sorry for us. It’s not an easy game. You’ve got to be a man about it, and turn the page.”

Follow Andy McCullough on Twitter: @McCulloughTimes