Sanchez tossed eight strong innings to win his first game in more than two months and the Marlins survived another ninth-inning homer from Jason Giambi to beat the Rockies 6-5.
"The most impressive thing about him tonight was the fact that all our runs were scored via the home run," Rockies manager Jim Tracy said. "We hit a ball out of the ballpark and he kept firing balls in the strike zone. He didn't back off."
Sanchez almost walked away with a no-decision when the Rockies faced Florida closer Leo Nunez.
A night after he hit a walk-off three-run homer, Giambi hit a pinch-hit two-run homer off Nunez with two outs in the ninth. Ty Wigginton followed with a single before Dexter Fowler popped out to end the game.
"We did what we could possibly do in the ninth inning," Tracy said. "We had the winning run standing at home plate, but we popped the ball up to end the game.
Sanchez (7-6) was sharp in earning his first victory since beating Arizona on June 10 and continued his dominance of the Rockies, who he nearly no-hit in April. He scattered five hits and struck out seven, improving to 3-0 in four starts against Colorado.
The Marlins gave Sanchez an early lead when they jumped on starter Jhoulys Chacin in the first inning. Petersen tripled with one out, Stanton walked and Greg Dobbs singled to make it 1-0. After a strikeout, Mike Cameron singled to left to give the Marlins a 3-0 lead.
Florida loaded the bases on two walks but Chacin got Sanchez to ground out to end the inning.
"After the first inning I got better throwing strikes," Chacin said. "Everything had been in the middle in the first. This is the big leagues. When you throw in the middle, they are going to hit you hard."
The Rockies got two back in the bottom of the second on solo homers from Tulowitzki and Seth Smith. It was Tulowitzki's 25th homer.
The Marlins stretched the lead in the fourth. Light-hitting Jose Lopez led off with a double and scored on Emilio Bonifacio's single to left. Petersen followed with his second triple to make it 5-2.
That was all for Chacin (9-10), who allowed five runs on eight hits, struck out four and walked three.
Gonzalez led off the bottom of the fourth with his 19th homer to cut the lead to 5-3.
Stanton hit his 28th homer to lead off the seventh.
The Rockies have lost five of their last seven and are 10 games under .500.
"This is getting worse. We need to start winning series and winning a lot of games," Gonzalez said. "It's the only way we are going to get out of this hole. These losses make things worse."
NOTES: Colorado RHP Juan Nicasio talked publicly for the first time since suffering a fractured vertebra after getting hit by a line drive on Aug. 5. ... Marlins INF Omar Infante (fractured right middle finger) will join the team in San Diego on Friday. ... The Rockies will send RHP Aaron Cook to the mound in the series finale Wednesday. Cook has lost his last two starts and has received little offensive support of late. The Rockies have scored just three runs in his last four starts. ... Ricky Nolasco will pitch for Florida on Wednesday. Nolasco needs just three strikeouts to pass Dontrelle Willis for first in club history in career strikeouts. ... Gonzalez has 11 hits since being activated from the 15-day disabled list on Aug. 6.