And for the third time in as many games, the Rockies' bullpen allowed the Pittsburgh Pirates to take a late lead en route to victory.
Andrew McCutchen hit a tiebreaking single in the seventh inning, Neil Walker followed with a home run and the Pirates overcame a three-run deficit to beat the Rockies 5-3 Sunday.
With the score 3-all, Matt Belisle (2-6) relieved and Harrison worked out a seven-pitch walk leading off the seventh. Harrison stole second and scored on a single by McCutchen, who then was caught stealing second. Walker followed with his 14th homer.
"Today was amateur, as far as what not to do," said Belisle, who got just two outs.
Belisle allowed two runs without pitching a full inning for the second time in Pittsburgh after he pitched one-third of an inning Friday night in Colorado's 4-2 loss.
"Matty's in there struggling right now," Colorado manager Walt Weiss said. "He's ready to go and his mentality is strong. He's struggling right now, like a lot of us."
The lack of performance from one of the Rockies' clubhouse leaders is one of many things going wrong for a last-place team that dropped a season-high 18 games below .500 at 40-58.
"I have to control what I can, but this business is about results, and I'm the first to abide by that," Belisle said. "You can't get away from the preparation or the type of teammate or leader that you have to be."
Jeanmar Gomez (2-2) pitched a one-hit seventh, All-Star Tony Watson struck out two in a perfect eighth and Mark Melancon pitched a 1-2-3 ninth for his 18th save in 21 chances.
"You've got to be a able to put games away, and it's frustrating," Weiss said.
Pittsburgh has two series sweeps this month after failing to sweep any during the first three months of the season. The Pirates took three in a row at home against Philadelphia from July 4-6.
Pirates starter Jeff Locke gave up three runs and seven hits in six innings, and Rockies starter Tyler Matzek allowed three runs, seven hits and three walks in six innings. The rookie struck out a career-high eight.
"Tyler did a great job," Weiss said. "Put us in position (to win) again. That's three good starts in a row by our starters, but (we) couldn't get the big hit to bust it open early."
Colorado built an early 3-0 lead on Josh Rutledge's two-run homer in the first and a Michael McKenry drive leading off the second.
Mercer had a two-run single in the bottom half, and Chris Stewart's second double of the game drove Mercer home in the sixth.
Pittsburgh had come from behind in 25 of its 52 wins.
"If you get too caught up in the score or too caught up in things that are out of your control, it's going to lead to pressing and trying to do too much," Walker said. "We do a good job of not doing that around there."
NOTES: Colorado didn't play 1B Justin Morneau (neck), SS Troy Tulowitzki (thigh) and OF Charlie Blackmon (ankle). ... Pittsburgh has won its first three games out of the All-Star Break for the first time since 2004. . RHP Edinson Volquez (8-6, 3.65 ERA) is to start Monday'sopener of a three-game series against the Dodgers. LHP Hyun-Jin Ryu (10-5, 3.44 ERA) is slated to pitch for Los Angeles. ... Colorado returns to Coors Field and opens a three-game series against Washington. LHP Franklin Morales (5-4, 5.26 ERA) starts for the Rockies and RHP Doug Fister (8-2, 2.90 ERA) for the Nationals.