DENVER — Chris Nelson was watching when Nick Masset looked down at the ground.
Talk about a heads-up play.
Nelson stole home in the eighth inning to send the Colorado Rockies to a 6-5 victory over the Cincinnati Reds on Thursday, completing a four-game series sweep and extending their winning streak to a season-best seven games.
With one out and runners on the corners, Nelson broke for home before Masset (3-4) threw his first pitch to Miguel Olivo. Inexplicably, Masset stepped off the mound, whirled to his left and toward second base.
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"He was just looking right at the ground," Nelson said. "He wasn't paying me any attention. (Third baseman Scott) Rolen was playing back. So I just decided I should just go ahead and go. I didn't stop."
Nelson scored easily to give the Rockies a 6-5 lead. He became the first player to take home for his first career steal since Dan Uggla of the Florida Marlins accomplished the feat on April 21, 2006, against the Philadelphia Phillies, according to STATS LLC.
The Rockies, who trailed 5-0 after two innings, had called for a suicide squeeze but it never got that far.
"Once I made up my mind I was going, I was going," Nelson said.
Masset, who had made 15 consecutive scoreless appearances, said he came set, stepped off the mound and initially thought Melvin Mora was going to second.
"I turned around and by the time I looked to third base the guy was halfway home and I didn't have a chance to get him," Masset said. "It was a complete mistake on my part. You should check the runner at third right away and go from that. I passed that because normally you get the guy at first who is trying to be sneaky. It was a complete mishap on my part. It is embarrassing, something that should never have happened, just something you never see before."
Reds Manager Dusty Baker said he had never lost a game in this fashion. It was the fifth consecutive loss for Cincinnati, which began the day with a six-game lead over St. Louis in the NL Central.
Troy Tulowitzki started the winning rally with a leadoff drive off Masset for his 18th homer and sixth in the past seven games.
"It was a fastball up," Tulowitzki said. "I'm a good fastball hitter. I got on top of it, and it went out."
Jason Giambi, who hit a two-run homer in the fourth, followed with a walk and was replaced by Nelson. First baseman Joey Votto, in the running for NL MVP, then made a critical error on Melvin Mora's slow bouncer. He charged the grounder, but his underhand flip to Masset covering first was high and wide.
Nelson went to third on the play, setting up the 15th swipe of home in Rockies history.
Huston Street allowed a leadoff single to Ramon Hernandez in the ninth, then struck out the side for his 17th save in 21 save opportunities.
The Rockies have won 10 straight games against the Reds at Coors Field and 19 of their past 22 games overall against Cincinnati.
Matt Belisle (7-5) recorded two outs in the eighth to get the victory.
Cincinnati got off to a nice start against Jason Hammel, who pitched seven innings.
Brandon Phillips singled, stole second and advanced to third on a wild pitch before scoring on Votto's swinging bunt in the first.
The Reds added four more in the second. Ramon Hernandez hit an RBI double and scored on Paul Janish's single. After Travis Wood sacrificed, Drew Stubbs hit his 16th homer and first since Aug. 14.
Hammel then settled down and pitched five scoreless innings, allowing three hits in that span.