Parra and Young homered off Colorado closer Huston Street in the ninth, then Justin Upton brought Young home with a bloop single in the 11th to give the Diamondbacks a stunning 3-2 victory over the Rockies on Thursday night.
"It took us 8 1/3 innings to start," Young said, "but it was nice."
Two nights earlier, Upton beat the Rockies with a booming home run. On Friday, it was a fly ball right fielder Seth Smith tried desperately to reach -- but he was playing too deep.
Young, who just missed a home run high off the overhang in left-center for a double, raced home for the game winner.
"It wasn't a hard hit by no means," Young said, "but with our team, sometimes if you just put the bat on the ball you will find holes. A lot of guys strike out in that situation but he was able to get the bat on the ball and make something happen."
The Diamondbacks finished their homestand 6-4, taking two of three from the Rockies and Philadelphia and splitting four with the Chicago Cubs.
"You just kind of hang in there," Arizona manager Kirk Gibson said. "You can't get discouraged."
Street blew his first save in 12 tries this season after Jason Hammel had thrown seven scoreless innings.
"You get beat sometimes. That's part of the game," Street said. "It's about brushing it off as an individual, as a team. You know, this is one of the first games we've lost in this fashion, maybe the first one all season."
Parra's one-out opposite field homer cut it to 2-1, then Young's two-out shot to left tied it.
"Just a mislocation on a slider," Street said of Young's blast, "definitely not where I was trying to put it, and he beat me on it."
"These gnaw at you," Colorado manager Jim Tracy said.
The Rockies were 1 for 12 with runners in scoring position.
In the top of the 11th, Johnson booted Carlos Gonzalez's sharp grounder to second for an error, then Troy Tulowitzki walked to put runners at first and second with no outs. Todd Helton, though, popped out, then Hernandez struck out Smith and Ian Stewart to retire the side.
Rafael Betancourt threw a scoreless eighth to set things up for Street, who fanned Juan Miranda for the first out. Parra followed with a homer on a 1-2 count. It was his second home run of the season but just the 10th in three major league seasons.
Still, pinch-hitter Xavier Nady struck out to put Street one out away from another save. But Young's eighth home run of the season tied it in front of the smattering of fans still on hand.
Colorado used seven pitchers, Arizona six.
Hammel allowed four hits, struck out four and walked three. The right-hander has allowed two runs in 20 2/3 innings in his last three starts.
Colorado's Dexter Fowler was 3 for 4, including a triple, and reached base four times.
Gonzalez made two standout catches in left field, both off the bat of Stephen Drew. The first was a diving grab of what would have been an extra-base hit, the second a foul ball up against the wall down the line.
Kennedy gave up two runs and six hits in six innings, walking three and striking out five. His wild pitch allowed the first run to score on Morales' sacrifice fly in the second inning.
Smith led off the second with a double on a hit Upton couldn't handle in deep right field. He took third on the wild pitch then scored on the fly by Morales, who was batting eighth in the order as catcher Chris Ianetta got the night off.
Helton started the fourth with a double, his 535th to move ahead of Lou Gehrig into 30th place on the career list. Morales' RBI single made it 2-0. Colorado went on to load the bases but Jonathan Herrera grounded into a fielder's choice to allow Kennedy to escape with minimal damage.
Drew was back at SS after missing a game with a sore groin. ... Hammel threw a season-high 114 pitches, settling down after 25 in the first inning, when the Diamondbacks left the bases loaded. ... Tulowitzki was 0 for 13 in the series. ... Betancourt was twice called for going to his mouth with his pitching hand.