SAN DIEGO -- After their strong start, the Padres faded quickly from contention early in the second half. They’ll get their chance to shake up the National League playoff picture anyway during the season’s final three weeks.

Beginning Monday, with a 10-2 loss to the Cubs at Petco Park, the Padres embarked on a stretch in which 17 of their final 20 games are against teams in the playoff hunt. No team in baseball has a better chance to cause chaos in the final month.

• Box score

The Padres would prefer to be fighting for a playoff spot themselves, of course. But for their development purposes, this is the next best thing.

As things stand, September is serving as an open audition for San Diego’s 2020 roster. There are places available in the rotation, bullpen, infield and outfield. Manager Andy Green has set his lineups accordingly.

In that regard, the Padres would prefer to be playing playoff-caliber opposition.

"For some of the younger guys in particular ... you want them facing teams that are highly motivated to go win every baseball game," Green said. "They're digging into scouting reports at a very deep level, and they're going to attack your guys a certain way. We want to see our guys combat that and win those situations."

They didn’t win many of those situations on Monday. Right-hander Cal Quantrill allowed eight runs on 10 hits in just 4 1/3 innings. He became the first pitcher since Tampa Bay’s Albie Lopez in 2001 to allow eight runs in three consecutive starts.

Quantrill’s recent struggles seemingly came out of nowhere. He’d posted a 1.79 ERA in his first seven starts after the All-Star break, establishing himself as a legit rotation piece. But his recent performance might have called that notion into question.

"Back to the drawing board," Quantrill said. “I’m not a quitter. I’ll figure it out.”

In fairness to Quantrill, his final line was a bit harsh. The Cubs took a 2-0 lead in the first on Nicholas Castellanos’ two-run homer. Quantrill’s pitch -- a fastball running in -- was executed where he wanted it.

After two scoreless frames, Quantrill fell victim to some seeing-eye hits in the fourth and fifth. They weren’t errors, technically, but both Manny Machado and Eric Hosmer let grounders get by them. Then, with a man aboard in the fifth, Victor Caratini hit a would-be double-play grounder to short. With the runner going, Luis Urias had vacated his position, and Caratini had a single instead.

Still, Quantrill refused to use any of that as an excuse for his performance.

“In big situations, I'm not making the pitches I need to make,” Quantrill said. “Earlier in the year, I was. Earlier in August, I was. I know that I can do it. Right now I'm not doing it. It makes it almost more frustrating.”

Quantrill isn’t the only Padre with a September audition. Left fielder Nick Martini went 3-for-5 to extend his hitting streak to a career-high eight games. He’s batting .371 since the Padres claimed him off waivers from Oakland late last month.

“Any time you go somewhere new or join a new team, you want to make a good impression,” Martini said. “I think it's definitely been good for me.”

Meanwhile, righty reliever Javy Guerra -- a converted shortstop -- bounced back nicely from his rough debut. He threw a scoreless seventh inning and reached 100 mph with his final pitch, striking out Castellanos to end the frame.

“That’s a really impressive arm,” Green said. “It was good to get him back on the mound. He gave up a couple baserunners, but he hung in and got a big punch out against a guy that’s been one of the hottest hitters in the game.”

By then, the game was out of reach. But Guerra’s outing Monday might have earned him an opportunity in a high-leverage spot against a quality opponent.

With series against the Cubs, Brewers, D-backs and Dodgers on the horizon, those opportunities should be plentiful.