SAN FRANCISCO -- On the 25th anniversary of Denver being awarded an expansion franchise, Nolan Arenado gave San Francisco Giants fans in the left-field bleachers a gift Tuesday night.

The game-used baseball from the historic night's biggest hit.

Arenado continued his powerful hitting against the Giants, blasting a three-run, seventh-inning home run that rallied the Rockies to a 7-3 victory.

"I hit that ball as good as I can hit a ball," Arenado said of his 23rd home run of the season, which turned a 2-1 deficit into a 4-2 lead.

"It was exciting. Especially here," he continued. "The crowd here can get loud. It was nice to quiet them down for five minutes."

Tyler Chatwood pitched effectively for five innings in his return from the disabled list, and the Colorado bullpen held the Giants to one run after that, allowing the Rockies to even the three-game series at a win apiece and the season series with the National League West leaders at 6-6.

The Rockies' six-man bullpen contingent included right-hander Adam Ottavino, who pitched in the majors for the first time since April 25, 2015. He returned from Tommy John surgery to retire the only batter he faced, Giants All-Star catcher Buster Posey, on a grounder to shortstop in the eighth inning.

"I just wanted in there," he gushed afterward. "I'm glad the way it worked out."

Madison Bumgarner shut out the Rockies on four hits over six innings before being lifted in favor of right-hander George Kontos to start the seventh. Bumgarner had thrown only 96 pitches, the second fewest he totaled in a start this season.

"We've been working him pretty good," Giants manager Bruce Bochy explained of the decision to get Bumgarner. "That's enough for him. He's human."

Mark Reynolds and Nick Hundley greeted Kontos with singles.

Two outs and two pitchers later, DJ LeMahieu's infield chopper went for an RBI single when Giants third baseman Conor Gillaspie's throw to first base was off the mark, allowing Reynolds to score Colorado's first run of the game.

Giants right-hander Cory Gearrin (3-1) then got two strikes on Arenado before leaving a slider in the heart of the plate, which the slugger deposited well into the left-field bleachers for a 4-2 lead.

"He's got a knack for doing it," Rockies manager Walt Weiss noted.

The homer was Arenado's 14th in 31 games against the Giants since the start of last season, the most by any player against a single opponent over that span. Arenado's 45 RBIs against the Giants over that stretch also are tops among major-leaguers.

"I love playing here," Arenado said of AT&T Park. "I've never been to the playoffs. When you play here, it's like a playoff atmosphere. I enjoy that."

In snapping a season-high, six-game losing streak, the Rockies broke the game open in the eighth, getting RBI singles from Hundley and Charlie Blackmon. Giants right-hander Hunter Strickland also walked in a run.

The seven runs were four more than Colorado totaled in the first four games of its trip.

Five Giants relievers were charged with seven runs on nine hits in three innings.

"We're going to meet and see if we can get this thing right," Bochy said of his bullpen. "We're trying to get this thing sorted out. At times they're really good. It's a matter of somebody stepping up and taking over a role."

Right-hander Jordan Lyles (2-2), the Rockies' second pitcher, got the win.

LeMahieu had three hits and two RBIs for the Rockies (38-45), who trail the Giants (53-33) by 13 1/2 games in the NL West.

Blackmon, Reynolds and Hundley added two hits apiece in Colorado's 13-hit attack.

Brandon Belt had two hits and Angel Pagan scored twice for the Giants, who had won four of five and were looking to go 22 games over .500 for the first time this season.

Mac Williamson, who earlier in the game made a spectacular sliding catch on Rockies shortstop Trevor Story with the bases loaded, capped the Giants' scoring with an RBI single in the bottom of the eighth.

Bumgarner, one of three Giants named to the NL All-Star team Tuesday, walked two and struck out six.

It was the fourth time this season that he pitched at least six innings and didn't give up a run. He got a no-decision this time after having won the first three.

Chatwood was pulled after five innings, having thrown 88 pitches in his first outing since June 18.

He gave up two runs (one earned) and lowered his best-in-baseball road ERA to 1.29. He allowed three hits and four walks while striking out four.

NOTES: Eight of 3B Nolan Arenado's 14 home runs against the Giants in the past two seasons have given the Rockies the lead. ... The Giants bullpen has blown 17 saves, tied with the Cincinnati Reds for the most in the majors. ... Giants C Buster Posey, LHP Madison Bumgarner and RHP Johnny Cueto, and Rockies RF Carlos Gonzalez and Arenado were named to the National League All-Star team. Posey was voted by the fans to be a starter. ... San Francisco (1B Brandon Belt) and Colorado (SS Trevor Story) both have players among the five in the online vote that will decide the final member of the NL team. ... In order to reinstate RHP Tyler Chatwood (back spasms) from the 15-day disabled list and RHP Adam Ottavino (right elbow surgery) from the 60-day DL, the Rockies demoted RHP Eddie Butler to Triple-A Albuquerque and placed RHP Justin Miller (strained left oblique) on the 15-day DL.