SAN DIEGO — The Phillies’ top three starters have been lights out lately.

Since Zack Wheeler returned to the rotation on April 25, Wheeler, Cristopher Sánchez and Jesús Luzardo have combined to go 10-1 in 17 starts with a 1.46 ERA and 0.88 WHIP. Opponents are slashing .192/.243/.269 against them.

Outstanding.

That kind of production has helped mask some of the inconsistency from the back end of the rotation.

The Phillies have recently gotten more from rookie right-hander Andrew Painter, who has a 2.60 ERA and 0.98 WHIP over his last three starts. The 23-year-old has made adjustments to his pitch mix and usage, which has helped him hit his stride as the Phillies continue to do the same under interim manager Don Mattingly.

The one rotation constant during their 18-8 stretch under Mattingly has been Aaron Nola’s struggles.

Nola will take the ball Tuesday night against the Padres at Petco Park. Through his first 10 starts, the Phillies’ longest-tenured player has a 6.01 ERA. He has allowed 61 hits in 50 2/3 innings. Only three of his outings have been quality starts — against the Rockies, Giants and Marlins.

Those three teams have a combined .415 winning percentage and .688 OPS this season.

San Diego may look like a tougher task at 31-22, good for the top Wild Card spot in the National League. But the Padres have produced a .657 OPS, the second worst mark in the Majors.

So, how can Nola bounce back?

THE SEQUENCE

The pitch that has hamstrung Nola in his 12th big league season has been his four-seam fastball.

Opponents are hitting .417 against it with an astronomical .958 slugging percentage. That opponent slug would be close to double his career high against the pitch.

Left-handed hitters have done the most damage, hitting .484 with a 1.065 slugging percentage and 97.2 mph average exit velocity.

It has not been a competitive pitch.

Luckily for Nola, he will face a Padres lineup with just two left-handed hitters, the fewest he has faced in a start this season. Gavin Sheets has posted a .902 OPS against righties. Jackson Merrill is batting just .194 against right-handers.

That could allow Nola to lean more heavily on his knuckle curve, which has been his most reliable weapon this year. Opponents have struggled against it from both sides. Right-handed hitters are batting .189 against the pitch. Lefties are at .229.

Nola threw the pitch on the first pitch seven times in his last start, six of them for strikes. He threw it for a strike at an 85 percent rate, a season high. If there was a positive from that outing, it was that.

The ability to throw the knuckle curve in any count helps him pitch backward. It can also open up more creativity with his changeup. Nola throws it only five percent of the time against righties, but it could become a strikeout pitch if he is ahead with two strikes.

For the first time in the Don Mattingly era, the Phillies drop a series after a 9-4 loss to the Reds on Wednesday afternoon.

LIMIT THE HEATER?

Nola is going to have to get creative if he moves away from the four-seamer.

It is a pitch this Padres lineup can damage.

Nola’s four-seamer averages 92.1 mph. San Diego’s hitters have slashed .289/.418/.467 against four-seamers at 92.1 mph or lower this season. Their average drops to .266 against four-seamers at 93 mph or lower and .236 at 94 mph or lower.

One pitch right-handed hitters have handled against Nola is the sinker. But the Padres have posted just a .715 OPS against sinkers and two-seamers.

Boring that pitch in on the hands of San Diego’s right-handed bats could help Nola induce softer contact, something he has struggled to do this year. According to Statcast, he is in the 32nd percentile among pitchers with a 41.9 percent hard-hit rate.

Tunneling the knuckle curve with the sinker against a mostly right-handed Padres lineup could be a key to a bounce-back outing.

STAY AHEAD

This can be said about any pitcher, but Nola’s numbers show a stark difference between pitching ahead and pitching behind.

When Nola gets ahead 0-1, hitters have a .314 on-base percentage. If the season ended today, that would still be a career high, but it has at least limited opposing bats.

When he falls behind 1-0, that OBP jumps to .388 with a .903 OPS.

And Nola cannot simply steal a first-pitch strike by catching too much plate.

Of the 25 balls put in play against Nola’s first pitch this season, he has allowed 11 hits, a .440 average and two homers. He carries a 7.71 ERA on the first pitch. That ERA has been north of seven in first-pitch situations over the past four seasons.

That circles back to pitch diversity.

Nola does not need to reinvent himself Tuesday night. But against a Padres lineup that has struggled overall and will not be stacked with left-handed bats, there is a path. It likely starts with fewer predictable four-seamers, more early-count curveballs and enough sinkers to keep righties from leaning out over the plate.

It is Schwarber’s 21st home run of the year, the Phillies first home run as a team since Wednesday the 20th!

NOTES

Mattingly will go with Kyle Schwarber in the leadoff spot Tuesday. Trea Turner will bat second. The Phillies’ interim skipper will give Adolis García “a day” and play Edmundo Sosa out in left field, with Brandon Marsh in right.

Turner is batting .115 over his last seven games with three hits in 26 at-bats. Schwarber, meanwhile, has a 1.204 OPS over his last 15 games. As Mattingly put it, moving him to leadoff gives the Phillies “boom out of the gate.”

The argument against Schwarber in the leadoff spot in the past has been that it can clog the basepaths for Turner. But right now, the Phillies’ shortstop is not getting on base enough to use his legs.

Until he does, giving the club’s hottest hitter a chance to provide thump at the top of the lineup makes sense. Schwarber’s big swings have been the difference plenty of times lately, especially working hand-in-hand with their dominant pitching performances.