Soler, a 22-year-old prospect from Cuba, was called up Wednesday after getting a nine-year, $30 million deal from the Cubs in 2012. He started in right field and batted fifth.
''He looked very comfortable in the box, as we were told about him before he got here,'' manager Rick Renteria said.
After Luis Valbuena led off the second inning with a homer off Mat Latos (5-3), Soler hit a 2-1 pitch into the Reds' bullpen in center field. The last Cub to homer in his first at-bat also did it in Cincinnati - Starlin Castro off Homer Bailey on May 7, 2010.
He said his father, Jorge Sr., was in the stands for his debut.
''I felt real proud he was here,'' Soler said, with a coach translating. ''I was very excited. I felt real comfortable.''
Soler also had an RBI single off Jonathan Broxton in the eighth, cutting it to 6-5. Latos pitched into the eight and gave up four runs while fanning a season-high 10 batters.
Pinch-hitter Chris Heisey homered in the bottom of the inning. Aroldis Chapman escaped a two-on threat in the ninth, getting his 28th save in 30 chances. Javier Baez flied out to the warning track in center to end it.
''Baez put a good swing on that ball,'' Renteria said. ''Everyone in the dugout thought it was going farther.''
Jacob Turner (4-8) made his first start for the Cubs and lasted only 3 2-3 innings, giving up six runs - three of them unearned.
''I would have liked to have gotten a little deeper into the game,'' he said. ''That part is frustrating.''
The Reds took advantage of three Cubs errors and ended their four-game winning streak, one shy of their season high. The Reds are 24-10 against Chicago over the last two years, including 10-5 this season.
The Reds sent nine batters to the plate and scored four times in the fourth inning, taking advantage of fielding errors by shortstop Starlin Castro and Valbuena at third. Schumaker, Brandon Phillips and Devin Mesoraco had RBI singles.
Reds leadoff hitter Billy Hamilton had a pair of infield singles and stole his 50th base, becoming the ninth Reds player to reach the mark. Bob Bescher holds the club rookie mark with 54 in 1909.
The Cubs were missing first baseman Anthony Rizzo, who has a stiff lower back. Rizzo hit his 30th homer during a 3-0 win on Tuesday night but had to leave in the eighth inning because of the back problem.
Cubs: Outfielders Ryan Sweeney and Justin Ruggiano went on the 15-day DL. Sweeney pulled a hamstring on Tuesday. Ruggiano hadn't played since last week because of a sore left ankle. INF Logan Watkins was recalled from Triple-A Iowa.
Reds: 1B Joey Votto took ground balls for the first time since he went on the DL on July 8 with strained muscles above his left knee. Manager Bryan Price said it's unlikely he'll start a rehab stint before Sept. 4, when he's eligible to be reinstated.
Cubs: Jake Arrieta (7-4) makes his second career start against the Reds. He beat them on June 24 at Wrigley Field, giving up two earned runs and three hits over seven innings of a 7-3 victory.
Reds: Dylan Axelrod (0-0) makes his second start of the season. He was the victim of a blown save on Aug. 17 in Colorado, a 10-5 loss.
Soler is sticking with the No. 68 that he wore in the minors, even though big numbers are not all that common in the big leagues. Asked about it before the game, Soler said through a coach translating: ''I don't know. I like that number.''
Hamilton's 50 steals are the most by a Reds player since Deion Sanders stole 56 in 1997. The club record is Bescher's 81 steals in 1911.
The Cubs have homered in 11 consecutive games for the first time since 2007. ... Valbuena's 13th homer gave him a career high, one more than his total from last season. ... Turner was acquired from Miami in a trade on Aug. 8 for a pair of minor league pitchers. He'd made two relief appearances with the Cubs. ... Chicago won a challenge in the fifth, when Kristopher Negron was initially ruled safe at first on a close play. The call was overturned on review. ... Heisey's homer was his third this season as a pinch-hitter and ninth career.
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