Arenado's ninth-inning walk set up Justin Morneau's tying double for Colorado, but Joey Votto led off the bottom half with a game-ending homer in Cincinnati's 4-3 victory over the Rockies on Friday.
Votto drove a 3-0 pitch from Boone Logan (1-1) over the wall in center for his fifth homer. Votto's fourth career game-ending shot traveled an estimated 437 feet.
Arenado went 0 for 3, ending his club-record and major league-best hitting streak. But he walked on a full-count pitch with one out in the ninth and Morneau then hit a drive into the gap in left-center, handing Jonathan Broxton (1-0) his first blown save in six opportunities.
"I didn't see many pitches to hit, and the ones I saw, I missed, but walks are a big deal to me," Arenado said. "I'm not a big walker. I was just doing what I could to help the team win."
Colorado manager Walt Weiss wasn't surprised at Arenado's selfless approach.
"He went up there with no other thought other than winning the game," Weiss said. "He was trying to get on base any way he could."
Johnny Cueto had another strong outing for Cincinnati, striking out eight in eight innings of two-run ball. The right-hander allowed five hits and walked one.
"That's the first time I've faced him," Arenado said. "He's got a sneaky fastball, and he locates it really well. He's one of the best pitchers I've ever seen."
Cueto has pitched eight or more innings in five consecutive starts. He has gone at least seven in each of his eight starts this season.
"The guys battled really well," Weiss said. "We knew it was going to be tough to score runs on Cueto. He's been locked in. We knew we had to scratch and claw. We had to battle every at bat and make him earn every out. They battled all the way through. Boone got into a tough count against a really good hitter."
Colorado's Jhoulys Chacin, making his second start of the season after missing the first month with a right shoulder strain, allowed two runs and four hits in six innings.
"Jhoulys did a hell of a job," Weiss said. "You could see his confidence growing every inning, especially with his fastball."
Skip Schumaker hit Chacin's second pitch of the game up the left-center gap for a double. He moved to third on Brayan Pena's groundout to first and scored on Brandon Phillips' sacrifice fly.
Todd Frazier drove Chacin's first pitch of the second inning 485 feet to a party area above the center-field batter's eye. Frazier's sixth homer of the season was the sixth-longest in the 12-year history of Great American Ball Park.
"The first two innings, I had trouble keeping my pitches down," Chacin said. "After the first two innings, I was trying to keep the ball down. I was using my sinker more. That's my game — throwing strikes and making them hit the ball into the ground."
Troy Tulowitzki led off Colorado's fourth with his 10th homer, a 404-foot shot on Cueto's first pitch that bounced off the roof over the Reds' bullpen bench in left-center field.
The Rockies tied it in the fifth. DJ LeMahieu led off with a single, moved to second on Chacin's groundout and scored on Charlie Blackmon's single up the middle.
Pinch-hitter Billy Hamilton greeted Logan with an opposite-field double down the right-field line in the eighth inning. Schumaker sacrificed Hamilton to third base, setting up Pena's sacrifice fly.
NOTES: Frazier extended his hitting streak to nine games, matching his career high. ... Weiss was pleasantly surprised that Morneau missed just one game with neck stiffness. Morneau, who has a history of neck problems, was scratched from Thursday's game at Texas, but started Friday at Cincinnati. "I didn't think it would be too long, but I thought it would be a couple of days," Weiss said. ... The Reds will most likely activate LHP Aroldis Chapman from the disabled list on Saturday, manager Bryan Price said. The team wanted to give the closer an extra day after he pitched on consecutive days for the first time on Tuesday and Wednesday to wrap up his rehab assignment. Chapman was struck in the left eye and nose by a line drive during a spring training game on March 19.