Scutaro smacked a 92 mph fastball from Casilla (0-2) just over the left-field wall for his first home run of the season after Colorado blew a three-run lead in the eighth.
Troy Tulowitzki, Michael Cuddyer and Carlos Gonzalez each drove in a run as the Rockies took advantage of three Giants errors to snap a four-game losing streak.
Rex Brothers (2-2) struck out Brandon Belt and Melky Cabrera with the bases loaded in the eighth. Rafael Betancourt struck out Nate Schierholtz looking with two on in the ninth for his seventh save in eight chances.
Solid outings by both starters were washed away.
Colorado's Jeremy Guthrie allowed four hits and one unearned run in 5 1-3 innings in his first start since April 22. He had gone on the disabled list after falling off his bicycle on the way to the ballpark last month.
Tim Lincecum lasted seven innings, striking out seven and walking three for the Giants.
PADRES 6, NATIONALS 1
WASHINGTON (AP) — Nationals ace Stephen Strasburg left after four innings, matching the second-shortest appearance of his 25-start career, and San Diego's Will Venable had four hits.
John Baker collected three hits and three RBIs for San Diego, which had lost four of five. James Darnell hit his first homer of the season.
Anthony Bass (2-4) — making his 10th start in the majors — tied his longest outing by going eight innings. He allowed five hits and one run — on Bryce Harper's homer to right-centre, the 19-year-old outfielder's second consecutive game with a solo shot. Bass didn't allow a hit until Ian Desmond's single in the fourth.
Strasburg (3-1) gave up four runs and seven hits, leaving after 81 pitches. He walked two batters and struck out five, and his ERA rose from 1.64 to 2.25.
CARDINALS 7, CUBS 6
ST. LOUIS (AP) — Yadier Molina hit an RBI single off second baseman Darwin Barney's glove with two outs in the ninth inning, helping the Cardinals avoid a sweep and an 0-5 homestand.
Matt Holliday and Matt Carpenter homered for St. Louis. Allen Craig had three hits and two RBIs and Tyler Greene snapped an 0-for-17 skid with three hits.
The Cubs tied it at 6 in the top half of the ninth on Alfonso Soriano's first homer of the season. Soriano hit 26 last year.
Holliday singled off Rafael Dolis (2-3) to start the bottom half and advanced on David Freese's one-out groundout. Molina's grounder to the right side deflected off Barney's glove and rolled into shallow right field, and Holliday scored without a play.
Jason Motte (2-1) got the win.
BRAVES 6, REDS 2
ATLANTA (AP) — Brian McCann homered and the Braves scored four runs in the third inning to deal Johnny Cueto his first loss.
Cueto (4-1) led the major leagues with his 1.12 ERA before giving up six runs, five earned, and eight hits in four innings. The right-hander had allowed only one earned run over 23 innings in his last three starts.
Tim Hudson (2-1) gave up two runs and nine hits in seven innings as the first-place Braves moved one-half game ahead of the Nationals in the NL East.
Michael Bourn had three hits and scored two runs and Martin Prado also had three hits for Atlanta.
Chris Heisey had three hits for the second straight game for Cincinnati. Ryan Hanigan went 2 for 4.
BREWERS 8, METS 0
NEW YORK (AP) — Zack Greinke ran his scoreless streak to 15 innings, Travis Ishikawa homered twice and Milwaukee earned a split of the two-game series.
Greinke (4-1) pitched five-hit ball for seven dominant innings. He pitched eight innings in his start last Wednesday but Milwaukee's bullpen was beaten by the Reds.
Ishikawa led off the fifth with his third homer of the year and connected for a three-run shot in the sixth, both drives coming on the first pitch of the at-bat against Dillon Gee (2-3). He also had a run-scoring groundout in the second inning as fog started rolling in, a misty haze that hung over the outfield for the remainder of the game.
Brewers second baseman Rickie Weeks homered to deep left in the seventh inning, snapping an 0-for-21 skid.
DIAMONDBACKS 5, DODGERS 1
LOS ANGELES (AP) — Wade Miley wiggled out of a couple jams while pitching into the seventh inning and the Diamondbacks snapped the Dodgers' five-game winning streak.
Miley (4-1) yielded eight hits and walked one in 6 2-3 innings, but limited Los Angeles to just one run on Mark Ellis' homer. The 25-year-old left-hander is 3-1 with a 2.35 ERA in five starts since being inserted into the rotation on April 23 to replace Daniel Hudson, who is out with a right shoulder impingement.
Ellis finished with three hits in the Dodgers' first game since star centre fielder Matt Kemp went on the 15-day disabled list because of a left hamstring strain. They still own the best record in baseball at 24-12.
Chad Billingsley (2-3) threw 77 pitches in four-plus innings and was charged with four runs and eight hits in his 200th regular-season game.
MARLINS 6, PIRATES 2
MIAMI (AP) — Marlins ace Josh Johnson allowed two runs over seven innings for his first victory in more than a year.
Johnson (1-3) had gone winless in 12 starts since his most recent victory on April 19, 2011. He missed the final 4 1/2 months of last season because of right shoulder inflammation.
Hanley Ramirez had three hits and two RBIs for the Marlins. Omar Infante tied a career high with four hits, including a two-run single, and John Buck singled home the other two runs.
The Marlins concluded a 3-2 homestand and split the two-game series.
Pittsburgh's Kevin Correia (1-4) lasted only 3 2-3 innings, his shortest outing this year, and gave up a season-high six runs. He fell to 0-4 in his past five starts.
PHILLIES 4, ASTROS 3, 10 INNINGS
PHILADELPHIA (AP) — Hunter Pence atoned for a ninth-inning error by hitting his second home run of the game, a solo shot in the 10th that lifted the Phillies to the victory.
Pence connected against former Philadelphia closer Brett Myers (0-1) with one out to give the Phillies their first three-game winning streak of the season.
Pence's bobble in right field while trying to make a throw home allowed Houston to tie it with two outs in the ninth.
The NL East champions ended a dubious drought with Pence's ninth homer of the season. This was the longest stretch of games (37) into a season without a three-game win streak for the Phillies since 1971, when they needed 51 games.
Jake Diekman tossed 1 1-3 scoreless innings to win his major league debut.