SAN DIEGO -- The Padres’ roller coaster 2019 season wound its way back to .500 on Wednesday afternoon. Only 100 games left to play.

The San Diego bullpen came unraveled in a series-ending 7-5 loss to Philadelphia at Petco Park. Josh Naylor and Wil Myers went deep to put the Padres in front early. But the Phillies rallied for three runs in the seventh to tie the game, before Adam Haseley and Andrew Knapp drove in runs against Craig Stammen in the eighth.

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With the loss, the Padres returned to .500 for the fifth time this year. They’ve only spent one day below par this season. Twice, they’ve reeled off five-game winning streaks after hitting that mark, and they’ll be looking for a similar response this weekend against the Nationals.

Here are three takeaways from this week’s series against the Phillies:

Tough decisions loom in the outfield

A week ago, the decision seemed obvious: When Franchy Cordero returned from his right elbow injury, Naylor would give way on the roster. Both are left-handed-hitting outfielders, and Cordero can play all three spots.

But Naylor is forcing the Padres to think twice. He homered on Wednesday and is riding a five-game hitting streak. In two of those games, Naylor came up big as a pinch-hitter. It’s easy to see the 21-year-old slugger as a valuable bench piece who would get an occasional start against a tricky righty.

“I just try to play hard every night and be the best I can be every night,” Naylor said. “I hope they see I’m working hard, trying to be the best player for the team.”

Of course, Franmil Reyes, Hunter Renfroe and Myers aren’t going anywhere. Manuel Margot has options, but it’s hard to envision the Padres demoting him. He’s struggled at the plate, but he’s also the only true center fielder on the roster.

As things stand, Naylor is probably still the odd man out. The Padres almost certainly wouldn’t carry six outfielders for an extended period, and Cordero is approaching full strength on his rehab with Triple-A El Paso.

“We’ll cross that bridge when we get there,” manager Andy Green said. “We have guys out there who are contributing and doing some really nice things.”

The bullpen needs a lot of work

Two months into the season, San Diego remains squarely in the National League Wild Card picture.

Clearly, these aren’t the same old Padres. It also isn’t the same old reliable Padres bullpen.

San Diego relievers have combined for a 4.42 ERA this season. Kirby Yates owns a 1.00 mark over 27 appearances, but the bridge to the Padres closer has been shaky.

“We’ve got enough down there to be successful,” Green said, and he left it at that.

On Wednesday, Green called on right-hander Trey Wingenter with the Padres leading by three in the seventh. Wingenter recorded two outs, but he allowed a walk and a triple to Cesar Hernandez. That brought Bryce Harper to the plate as the tying run.

Without a reliable left-hander in the bullpen, Green called on Stammen. Harper roped an RBI double, then scored a batter later when Jean Segura bounced a single through the middle.

There’s never been a better time for this bit of welcome news: lefty relief ace Jose Castillo is likely to begin a rehab assignment at some point in the next week. He struck out 52 hitters in 38 1/3 innings last season, but he has missed the first two months with a flexor strain in his left forearm.

The young starting pitchers need to step up

Left-hander Matt Strahm served as the de facto veteran in the Padres’ Major League youngest starting rotation. He’s 27.

Now, Strahm is headed to the injured list with soreness in his rib cage. The Padres don’t think it’ll keep him out for very long. But the season is at something of a crossroads this week, and the team is currently relying on five starters age 25 or younger.

One of those starters is Cal Quantrill, who was recalled on Wednesday, then was sharp over five innings of two-run ball. The 24-year-old right-hander struck out seven and didn’t allow a walk. He almost certainly pitched his way to another start next week.

“He pitched very, very well today,” Green said. “That’s always something that’s going to earn you more opportunity -- when you throw the baseball like that. We need young guys to step up right now.”

Added Quantrill: “There was opportunity at the beginning of the year, and there is now. You’ve got to go out and earn it, and I’m doing my best.”

Lately, he’s making an impressive case. Quantrill has served as the “yo-yo” between Triple-A and the big leagues as the Padres have fluctuated between a five- and six-man staff. In Toronto last month, he struck out nine and allowed three runs on two hits over six innings. He was optioned afterward, only to be recalled after the minimum 10-day Minor League stint.

“Yeah, it kind of stinks going up and down, but that’s my role right now,” Quantrill said. “I’m coming out with intensity, trusting the fact that I can win at this level and trying to give the Padres the best chance to win every game.”