It was the most runs the Rockies have allowed in a nine-inning win this season and something of a flashback to the sort of games that used to unfold regularly at Coors Field before the installation of a humidor for game balls in 2002.
"It's calmed down a little," Padres manager Bud Black said. "But that turned back the clock today."
The Rockies erupted for seven runs with two out in the third against Casey Kelly, who was making his second Major League start and lasted 5 2/3 innings. The uprising included a two-run double from Jordan Pacheco, who had two hits and extended his hitting streak to 11 games, matching his career high. Tyler Colvin and Ramon Hernandez each hit two-run homers in the inning, the 17th homer for Colvin and fifth for Hernandez.
Chase Headley drove in a career high six runs for the Padres while going 4-for-5 with his 23rd home run. And No. 8 hitter Alexi Amarista went 5-for-5 with two RBIs, setting a career high and becoming the first Padres player with five hits in a game since Headley did it in an 11-inning game in September 2009.
"We beat a ballclub... that's playing some of the better baseball in the industry," Rockies manager Jim Tracy said, referring to the Padres winning eight of their past 11 games and 17 of 26.
Nelson had a dismal day before his home run off Brad Brach, who was brought in to face him. In three previous at-bats, Nelson had been hitless, although he did reach base when second baseman Amarista bobbled his grounder ahead of Herhandez's home run in the third.
To make matters worse, when fielding speedy Cameron Maybin's grounder in the fourth, Nelson took too many steps before throwing, and that became a leadoff single in a three-run inning.
Nelson came up in the seventh after left-hander Tommy Layne hit Carlos Gonzalez with a pitch and Pacheco singled. Tyler Colvin sacrificed the runners with Nelson watching.
"It's things you dream about as a kid," Nelson said. "I was dreaming about it in the on-deck circle."
Nelson drove Brach's 1-1 slider over the fence in straightaway center. He said he was thinking triple when he broke from the batter's box and raised his fist in triumph when the ball vanished.
"I was just trying to hit something to the outfield to get the run in and it worked out for the best. I was thinking middle [of the field] the whole way," Nelson said. "The day wasn't going the best. Had a ground ball hit to me at third that Maybin beat out. Had a strikeout. To hit the home run, it all came out at once."
Brach said, "I was just trying to go slider down and away to slightly out of the zone. Just left it up, and he put a good swing on it and hit it out."
The Rockies tacked on what turned out to be a vital run in the eighth when pinch hitter Charlie Blackmon walked and scampered to third on Brach's errant pickoff throw. Dexter Fowler followed with an RBI single.
Starter Jeff Francis gave up six runs, five earned, in 3 2/3 innings and allowed 10 hits, tying his season-high June 9 in his 2012 debut for the Rockies against the Angels that lasted 3 1/3 innings.
Headley hit a two-run homer in the first following Forsythe's single. And Headley singled home Forsythe in the third, after Francis hit him with a pitch and Forsythe stole second.
Some of the trouble Francis found in the three-run fourth was not his doing. After Nelson was late throwing Maybin's grounder, Amarista followed with a single, and both runners moved up when left fielder Carlos Gonzalez bobbled the ball.
With one out, Francis gave up a two-run single to Denorfia. Gonzalez made an ill-advised throw home, allowing Denorfia to take second. He scored on Headley's two-out single, an eight-pitch at-bat that finished Francis.
"They hit some mistakes," Francis said. "But the one that knocked me out of the game, the at-bat to Headley, I was battling hard and he was waiting for me to put one in the middle and jumped at it.
"That inning we want to have a quick one. It got away from us a bit. But we maintained the lead... To win a game like today is a huge boost for us."
The Rockies have won 14 of their past 20 games. They went 5-2 on their last road trip to New York and Chicago and now face a more formidable seven-game jaunt to Atlanta (four games) and Philadelphia.
"We've got a road trip to two very difficult places," Tracy said. "But it's really, really good for our kids to go out on the road... to help continue to build character and play under duress you cannot simulate in Spring Training or in the Minor Leagues."