Morales (2-1) struck out seven, including a well-planned and powerful one with his final pitch against Angel Pagan with a runner in scoring position.
It also took a nail-biting bullpen performance, with big sequences from Rex Brothers, who induced a Pablo Sandoval double-play grounder to end the eighth, and LaTroy Hawkins (6-for-6 on save chances), who survived a walk and a hit with one out in the ninth. Big swings by Tulowitzki to open the fourth and Arenado to open the fifth against Giants starter Madison Bumgarner (2-2) helped.
But Morales leaving the mound with a triumphant fist pump and scream after fanning Pagan, for a third time, was the image of the night.
"I knew I was going to do the strikeout with Pagan," said Morales, whose work helped the Rockies win the series with the Giants (which concludes Wednesday afternoon) and improve to 8-3 at Coors field. "What I did all game was fastball away. Then I said, 'OK, it's time to throw my cutter down and in.' He wasn't looking for that pitch."
The Rockies acquired Morales -- who broke in with them in 2007 -- from the Red Sox this winter for infielder Jonathan Herrera, mainly because of Morales' versatility. After two mixed starts this season, Morales went to the bullpen briefly when Tyler Chatwood came off the disabled list. But after lefty Brett Anderson broke his left index finger, Morales was reinserted into the rotation after one relief appearance.
In two starts -- a win at San Diego and Tuesday night -- he has proven there's more to him than an arm the Rockies can shuttle back and forth. Morales has combined for 13 innings with 12 strikeouts, nine hits, two earned runs and three walks in the victories, both over National League West foes. The only run Tuesday was a homer by Hunter Pence with two out in the fifth.
Morales has left behind the mindset of proving himself as a starter, even though that is his clear ambition, and he wasn't impressed that Tuesday matched his June 28, 2012, performance for Boston at Seattle for his longest outing. All that personal stuff is less important than the competitiveness Morales is exuding on a team that has no other player who can say he was part of a World Series champion (with Boston last year).
"That guy has been in two World Series already [also with the Rockies in 2007] and three playoffs," said catcher Wilin Rosario, who joyfully called for Morales' fastball much of the night. "He knows how good that is.
"This guy is fun to have on the team. He knows how to compete. In those moments, when the emotion comes to your mind, your body, and your heart is pumping really quick, he gets it."
The Rockies (12-10) have had big homestands and hot streaks early in a season before. Heck, they were near the front of the NL West in June last year but finished 74-88. But for Morales, it's a feeling that games like Tuesday can help the Rockies capture and keep that grip through the year.
"We got a good team here, great family," Morales said. "Everybody is together. We try to stay on the same page every day when we come to the ballpark. We do a great job."
Maybe a family that lives by the fastball on both sides of the plate wins together.
"Most hitters want fastballs, and when you can make your fastball move one way or the other, you get a lot of bad contact," Rockies manager Walt Weiss said.
Morales used the two-seamer to his arm side and the cutter to the glove side, and set up some nasty other pitches -- a split-finger he used when Buster Posey grounded out to end the fifth, and the occasional curveball. With a bullpen that has been used often in high-scoring games this homestand, Weiss wanted at least six innings. Morales gave him one beyond that, using 99 pitches.
"They've been throwing the ball well," Giants manager Bruce Bochy said. "They did yesterday, they did today. We had our chances."
The surging Tulowitzki ended up almost as big a figure in the victory as Morales.
Pablo Sandoval doubled and Brandon Belt drew a walk with one out in the fourth. Joaquin Arias hit a ground ball toward the middle, but Tulowitzki made a diving play and forced Belt at second. Morales then induced a popout from Ehire Adrianza.
Tulowitzki opened the bottom of the fourth with his third homer of the year, to left field against Giants starter Madison Bumgarner (2-2), who went eight innings, gave up nine hits and fanned six against one walk. It was Tulowitzki's seventh RBI in five games this homestand.
Arenado opened the fifth by homering for the second time in as many games in the No. 2 slot in the batting order with Michael Cuddyer (left hamstring) on the disabled list. "[Bumgarner] was throwing good against me," said Arenado, who extended his career-best hit streak to 13 games. "I missed a couple of pitches. In that at-bat, I missed a couple pitches, too. Then, luckily enough, he left one over the plate."
Bumgarner, who had a grand slam in a win over the Rockies earlier this season, doubled off Morales with two down in the seventh, before Morales fanned Pagan.