"It was an unfortunate sequence there," manager Clint Hurdle said. "They plated three runs, they took advantage of balls up over the plate and found gaps."
A throwing error by Morton (8-6) in the sixth enabled the Rockies to scored two runs and extend their lead to 5-0.
With two outs and runners on first and second, rookie catcher Dustin Garneau hit a tapper between home plate and the pitcher's mound that Morton fielded. He then made an underhand toss that sailed over first baseman Michael Morse's head.
"I didn't realize how much time I had," Morton said. "I had no idea, my head's down, I'm going after the ball. I managed to throw it over a guy that's 8-feet tall."
Morton allowed five runs — three earned — and six hits in six innings. He walked two and struck out six.
The sinkerballer said he thought he made only one mistake when he threw a fastball down the middle to LeMahieu, but that the other hits came off pitches he executed.
"Obviously the result wasn't what I wanted, but I threw the ball where I wanted, Morton said. "I got hurt on one pitch and that was that pitch, the first pitch."
De La Rosa (8-6) allowed four hits in six-plus innings while striking out seven and walking one. The left-hander's only other win since July 11 — a span of 10 starts — came Aug. 7 at Washington.
"I've been pitching pretty well lately, but we just haven't been winning the games I've been pitching," De La Rosa said. "It feels good to have that win next to my name."
De La Rosa and manager Walt Weiss were ejected for arguing with home plate umpire Jeff Nelson as Weiss went to the mound to remove De La Rosa from the game.
"I got crazy there and started screaming at the ump," De La Rosa said. "He missed a couple of pitches but the umpires are human, too. I can't react like I did. I can't be out there screaming out at them."
Paulsen and center fielder Charlie Blackmon each had two hits for the Rockies, who won for just the fifth time in 19 games while avoiding being swept in the three-game series.
"You never want to get swept," Weiss said. "We played a really hot team tough and Jorge did a good job of making sure we got at least one (win) here."
The Pirates had their four-game winning streak snapped and lost for just the fourth time in 18 games. Jordy Mercer had two of the Pirates' four hits.
Pirates: RHP A.J. Burnett (strained flexor tendon in right elbow) threw a 71-pitch bullpen session prior to the game and said he hopes to be activated from the disabled list sometime during the four-game home series against the Chicago Cubs from Sept. 15-17.
DAY OF REST
Rockies shortstop Jose Reyes was not in the lineup as he was rested in a day game following a night game. It was the fourth time he did not start in 30 games since being acquired from Toronto in a trade July 26.
Rockies: RHP Chad Bettis (6-4, 4.69 ERA) will face Arizona LHP Robbie Ray (3-10, 3.86) on Monday night in the opener of a four-game home series. Bettis has allowed six runs in 2 1-3 relief innings in his career against the Diamondbacks.
Pirates: Following Monday's off day, RHP Gerrit Cole (15-7, 2.44) will start Tuesday night in the opener of a three-game series at Milwaukee against RHP Jimmy Nelson (10-10, 3.81). Cole was originally scheduled to pitch Wednesday but was moved up a day so he can start next Sunday night against the NL Central-leading Cardinals at St. Louis.