Iannetta hit a two-run homer off Anthony DeSclafani in his return to the mound, and Gonzalez added an impressive three-run sho t Tuesday night, powering the Colorado Rockies to a 9-6 victory over the Cincinnati Reds.
The Rockies ended a four-game losing streak that was their longest since they dropped eight in a row last June. They'd blown a lead in all four losses, and wound up using their closer to finish it off after leading 9-1 on Tuesday.
''Our offense exploded for us and put up a lot of runs early and didn't stop,'' said left-hander Kyle Freeland (6-5), who allowed three runs while pitching into the seventh and got his first RBI of the season with a bases-loaded walk.
The Reds matched the third-worst start in franchise history at 21-40 despite getting one of their top pitchers back from his latest major injury.
DeSclafani (0-1) was projected as the Reds' top starter before he missed all last season with a strained pitching elbow and the first two months of this season with a strained oblique. He was activated off the disabled list before the game and got hit hard at the outset.
Charlie Blackmon had an RBI triple in the first inning and scored on Gonzalez's infield single. Iannetta hit a two-run homer in the second.
''The first two innings were definitely not the way I wanted them to go,'' said DeSclafani, who lasted five innings. ''I was excited to be back out there, but I've got to get off to a better start. We can't be in a hole that early.''
Gonzalez connected off Wandy Peralta on a 473-foot hom er that was the longest at Great American Ball Park since 2014 and put the Rockies up 9-1 in the seventh. Gonzalez also singled twice, giving him at least three hits and four RBIs in a game for the first time since 2016.
''Now you're seeing him come back and play in true CarGo form,'' Iannetta said. ''It's fun to watch.''
Freeland went 6 2/3 innings, allowing Scott Schebler's solo homer in the fifth and Tucker Barnhart's bases-loaded single in the seventh. Bryan Shaw gave up three runs in the ninth before Wade Davis fanned Scott Schebler for the final out and his NL-leading 19th save in 21 chances.
Rookie outfielder Mike Tauchman was called up from Triple-A Albuquerque and infielder Daniel Castro was optioned. Tauchman opened the season with Colorado and went 1 for 23. He pinch hit and walked.
Reliever Jackson Stephens was optioned to Triple-A Louisville to open a spot for DeSclafani. Right-hander Kevin Kevin Shackelford was released.
Blackmon had three hits, extending his hitting streak to a season-high 12 games.
Gonzalez's 473-foot homer tied Wily Mo Pena and Ryan Ludwick for the 16th-longest in GABP history. Adam Dunn hit the longest, a 535-foot drive off the Dodgers' Jose Lima in 2004 that cleared the ballpark and bounced into the Ohio River.
Gonzalez threw out Tucker Barnhart as he tried to stretch his hit to right field into a double leading off the fourth inning. Left fielder Gerardo Parra nailed Jesse Winker at the plate as he tried to score from second base on Joey Votto's single in the seventh, with the call upheld on review.
The Reds had 17 hits in a nine-inning game and lost for the first time since a 15-11 loss at San Diego on Sept. 5, 1984.
The Reds' worst 61-game starts: 19-42 (1934), 20-41 (1950) and 21-40 (1931, 2018).
Rockies: Ianetta was in the lineup after being forced to leave a game Sunday after a ball hit him in the thigh, causing numbness in the leg. He went 1 for 3.
Reds: Center fielder Billy Hamilton got a day of rest. He's in a 1-for-14 slump.
Rockies: Jon Gray (5-6) is coming off his shortest start. He lasted only 3 1/3 innings of a 7-4 loss to the Giants, giving up four runs on six hits. He's 3-0 career against the Reds with a 4.08 ERA.
Reds: Sal Romano (3-6) lasted 5 1/3 innings and gave up five runs during a 6-2 loss in Denver last Friday. He's 1-1 career against Colorado.
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