With the win, the Rangers claimed the Silver Boot trophy for the sixth straight year. They have won four of their last five games against the Astros and five of six overall.
"He threw strikes. He had good poise out there," manager Ron Washington said of Grimm. "He was dealing with a lot of butterflies that first inning. He settled down and followed Mike [Napoli's] lead. He did a great job for us. He really did. Kept us through six, kept us in the ballgame."
Grimm allowed three runs on six hits over six innings, striking out seven -- including five straight at one point -- without walking a batter. He threw 88 pitches, 56 for strikes, and left the game with the Rangers trailing, 3-0, before they rallied in the sixth.
"He did a great job," Napoli said. "He kept getting ahead of hitters and into two-strike counts. He was making his pitches and really trying to put them away. He didn't seem too nervous, he was just being himself."
"Give credit to the hitters. They came through for me," Grimm said. "My breaking ball was working tonight. I think that was in the difference. I was able to throw it behind in the count and when I was ahead."
After the Rangers failed to score in the first five innings, Craig Gentry and Ian Kinsler both singled to start the sixth-inning rally before Elvis Andrus moved them up with a sacrifice bunt. Then Michael Young hit a comebacker to Astros starter Lucas Harrell, who got Gentry in a rundown between third base and home. But catcher Chris Snyder bobbled a throw from third baseman Chris Johnson and everyone was safe.
"That was my fault," Harrell said. "I should have looked him back to third and then gone to first to get the out. I made the wrong decision, so it really cost us."
That left the bases loaded for Adrian Beltre, who delivered a two-run single to left field, driving in Gentry and Kinsler. On Harrell's next pitch, Cruz hammered a 94 mph fastball 431 feet into the Astros' bullpen in left field, giving the Rangers a 5-3 lead.
"We've done a very good job the last few series getting a clutch hit when we need it," Cruz said. "Everything started to come together -- hits, great baserunning by Gentry, a good hit by Beltre, and I was just looking for something in. That was the pitch he was throwing in the at-bats before. I was able to drive it."
Grimm, who was called up from Double-A Frisco to make this spot start, did not wait long to surrender his first run as a big leaguer. He gave up a leadoff single in the first to Jordan Schafer, who was caught stealing two batters later. But Jed Lowrie sent the next pitch Grimm threw over the wall in right field.
"For a kid making his debut, they usually have some nerves," Astros first baseman Brett Wallace said. "But after Jed homered, he settled in and really made some pitches when he needed to, got out of some jams and kept guys off-balance."
Grimm bounced back nicely. He struck out the next five batters, becoming the first player in Rangers history to strike out five straight batters in his Major League debut.
"He did a great job of keeping his composure after that home run," Rangers reliever Mike Adams said. "You don't expect it but some guys are born with that quality. He did a great job after that and did what we ask all of our starters to do -- throw strikes, keep us in the game, and let the offense do their job."
Grimm also became the first player with at least seven strikeouts and no walks in his Major League debut since Stephen Strasburg whiffed 14 without a walk in a win over the Pirates June 8, 2010.
"I can't even compare myself to that guy," Grimm said. "He's got some really good stuff. He knows how to pitch. To me, I'm still in my learning process. I'm still developing."
When asked if Grimm had earned another start as a big leaguer, Washington didn't have a definitive answer but remained impressed by the rookie's performance.
"He performed," Washington said. "Because he performed, he's in consideration."