DENVER -- Dexter Fowler's strong defense and confident swing sent the Colorado Rockies to a rain-soaked victory.

Fowler made a leaping catch early in the game and hit a sacrifice fly in the bottom of the ninth inning to help Colorado overcome a tying, three-run homer by Pedro Alvarez in a 5-4 win over the Pittsburgh Pirates on Monday night.

Fowler extended his tear at the plate with his 14th hit in seven games, but it was an out that won it for Colorado.

Wilin Rosario led off the ninth with a single against reliever Jason Grilli (1-3) and moved to third on a one-out single by pinch hitter Jason Giambi. Fowler hit a deep fly to Andrew McCutchen in center field and Rosario slid home ahead of the throw.

"I knew he was going to throw me a lot of sliders, but I was waiting on a fastball and he threw me one," Fowler said. "We knew we were going to put something together."

The Rockies were ready to celebrate an easier win an hour earlier when weather and Alvarez disrupted that plan.

Intermittent rain, heavy at times, fell throughout the night and finally prompted a 53-minute rain delay with one out in the top of the ninth and Colorado leading 4-1. McCutchen and Neil Walker singled off closer Rafael Betancourt, and with Alvarez at the plate the tarp was brought out.

"It's just tough because you've got to sit down for so long and resume play like nothing happened," Alvarez said. "You've got the adrenaline going before the rain delay and you just get kind of stagnant."

After play resumed, Alvarez hit reliever Rex Brothers' first pitch, a 98 mph fastball, into the left-field seats to tie the score at 4.

"A guy like that, you've got to try not to do too much and try to work with what he gives you," Alvarez said after his 18th home run. "I was just trying to go up there and try to get on base."

Brothers (5-2) got the win despite serving up the tying homer.

"I threw my best pitch and he put a swing on it," Brothers said. "The main thing was we got out of that inning and won it in the bottom."

Walker had three hits and McCutchen added two for the Pirates, who have lost three of four.

"For the fans that stuck around, that was a pretty exciting last 20 minutes," Pirates manager Clint Hurdle said. "I was very happy with the battle back. You never know what's going to happen."

Earlier in the game, Fowler used his glove to save the Rockies when he ran down Rod Barajas' deep fly at the wall in center to end the second inning.

"He told me he's glad he's not playing in the NL West anymore so I can't rob him," Fowler said. "That's a good feeling. It's always a good feeling to help the team."

The Rockies were held in check by Pittsburgh starter Jeff Karstens until they broke through in the fifth. Tyler Colvin led off with walk, Rosario singled him to third and Josh Rutledge drove in Colvin with another single.

Eric Young Jr., batting for starter Jeff Francis, drove a two-run double off the scoreboard in right field to make it 3-1. Young scored on Marco Scutaro's single.

Francis allowed one run and six hits, struck out one and didn't walk a batter in five innings.

Karstens was cruising before the fifth, retiring seven straight and allowing just three baserunners. He also contributed at the plate in the fifth.

With one out and Alvarez on first, Clint Barmes singled to left and Karstens followed with a grounder that bounced near the plate and over first baseman Michael Cuddyer for an RBI single to make it 1-0.

"I was trying to see the ball deep and hit it the other way," Karstens said. "I got lucky. I was thinking, I hope he can't jump."

It was Karstens' first RBI this season and the third of his career.

The right-hander allowed four runs and six hits, struck out four and walked two in seven innings.

Game notes
The Rockies said INF Chris Nelson was admitted to a hospital to undergo tests for an irregular heartbeat and will remain hospitalized overnight. ... The Pirates activated outfielder Alex Presley from the seven-day concussion disabled list and optioned first baseman Matt Hague to Triple-A Indianapolis. ... Rockies RHP Juan Nicasio had surgery on his left knee and will likely miss the rest of the season. ... Walker extended his hitting streak to 16 games. ... The Pirates will send LHP Erik Bedard (4-10) to the mound against Rockies LHP Christian Friedrich (5-6) on Tuesday.