CINCINNATI -- It's almost hard to believe. Reds starter Luis Castillo, who was named an All-Star in 2019 based in part on his scorching first half, is now winless seven starts into his ‘20 season.

As has often been the case, Castillo pitched well enough to win but just poorly enough to lose. During Sunday's 10-1 Reds loss to the Cubs, which split the four-game series, he gave up three home runs. They accounted for all four earned runs allowed over five innings with five hits, one walk and seven strikeouts.

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"We’ve got to be better for Luis. This is a team effort," Reds first baseman Joey Votto said. "There is no one person, but it’ll flip. He’ll have his big games. We’ll have big games behind him. Things will change. It just so happens he’s paid a price and we’ve paid a price collectively when one of our best guys goes out there and starts in Luis."

It was a scoreless game when Kyle Schwarber led off the fourth inning against Castillo by hitting a 2-0 changeup for a homer to right field. Two batters later, Jason Heyward deposited a 2-2 changeup over the right-field fence to make it a 2-0 game.

"It was pitches we didn't locate well," Castillo said via translator Jorge Merlos. "We didn't execute well, so they just hit home runs off of me that inning."

Nico Hoerner was grazed by a 2-2 fastball to open the fifth and was awarded first base after the Reds' replay challenge was unsuccessful. Ian Happ was down in an 0-2 count when he lifted a slider to right-center field for a two-run homer and a 4-0 Chicago lead.

Robert Stephenson gave up solo homers to Heyward and Happ. In the ninth, José De León walked the bases loaded and Schwarber became the third Cubs hitter with two homers on the day -- this time, it was a grand slam to right field.

Castillo is now 0-5 with a 4.10 ERA. What makes his winless stretch odd is that he isn't exactly struggling in most of his starts.

"I'm glad that I'm healthy right now and I'm able to pitch as well as I am, but there's always that one inning that just costs me a couple of runs, and it's just something that happens throughout the game," Castillo said.

Castillo has also been trying to become less predictable. He came in using his well-reputed changeup 32.4 percent of the time, according to Statcast, and that's consistent with the 32.5 percent it was in 2019. But hitters came in batting .231 against it this season, compared to .128 in '19.

On Sunday, Castillo used his changeup 13 times in 93 pitches, or only 14 percent of the time. He got just one swing and miss and no called strikes.

"Last year, we threw a lot of the changeups, which meant the batters got to see a lot of it," Castillo said. "I think this year they're just not hitting it as much, which is why I'm working so much on the slider to get it right."

There has been some bad luck mixed in for Castillo as well.

• Cincinnati has lost six of Castillo’s seven starts this season, while scoring just 15 runs for an average of 2.1 runs of support. The club was shut out twice when he pitched. It nearly became a third time on Sunday, but Votto hit his second home run in two days when he opened the bottom of the sixth by lifting José Quintana's 3-2 pitch just far enough over the wall in center field.

"[Castillo is] a great teammate and goes out and does his job," Reds manager David Bell said. "For the most part, he’s been really strong all year. He gives us a chance when he’s out there, more than a chance. He’s an excellent pitcher. It will come around. Our offense is definitely coming around. It didn’t happen today."

• According to Statcast, Castillo’s opponents' batting average of .269 was 63 points higher than his expected batting average (xBA) of .206. That is the largest discrepancy this season (minimum 100 batters faced).

• Castillo entered the day with his average fastball velocity up a full mile per hour from last season (97.4 mph in 2020 vs. 96.4 mph in '19). According to MLB Network research, that ‘20 average was the fifth-highest among any starter this season, trailing Jacob deGrom (98.5), Sixto Sanchez (98.2), Dustin May (97.8) and Dylan Cease (97.6).

• Although the defense behind him was clean on Sunday, he has allowed six unearned runs -- the most in baseball.

"I know I’ve made some errors at really, really crucial times that tacked on pitches and tacked on runs," Votto said. "I’m never going to speak on my teammates, but we definitely have to be better when our best guys are out there."