Shota Imanaga stellar in major-league debut as Cubs beat Rockies 5-0 in home opener

Cubs fans rose to their feet in the stands in the sixth inning Monday at Wrigley Field as left-hander Shota Imanaga stepped back up to the pitching rubber. Their whistles and cheers told of the excitement of the moment.

Imanaga fired a fastball across the lower third of the strike zone. Rockies hitter Nolan Jones whiffed, and Imanaga shouted in celebration. That strikeout wrapped up an impressive major-league debut for Imanaga as the Cubs beat the Rockies 5-0 in their home opener.

‘‘It was a unique atmosphere, especially in the last strikeout,’’ Imanaga said through an interpreter. ‘‘And it might have not been the best pitch with regards to pitch speed, but getting the support from the fans, I was able to get that strikeout.’’

As Imanaga walked off the field, he slapped his left hand across his chest. The roar of the crowd swelled.

Imanaga finished with nine strikeouts in six innings, becoming the first Cubs pitcher and the second in the majors in the modern era (since 1901) to hit those marks in his debut. He held the Rockies hitless until the sixth, when he gave up a pair of innocuous singles.

Imanaga pushed himself to 92 pitches, giving the Cubs the length they needed after the bullpen had to shoulder the burden of three consecutive games in which the starter was out before the end of the fifth.

‘‘Going out there, it was clear that this is a player who’s been in big moments and has been through this before,’’ manager Craig Counsell said. ‘‘That was part of what went into all this. But he quickly just got into competing.’’

As far as big moments go, Imanaga started for Team Japan against Team USA in the final of the World Baseball Classic last spring. But his start Monday opened a new chapter of his career. And he did so in front of an announced attendance of more than 40,000.

Through the first five innings, Imanaga allowed only one baserunner. Former Cubs star Kris Bryant hit a line drive that glanced off third baseman Christopher Morel’s glove for an error in the second.

Imanaga battled into some deep counts. Right after Bryant reached, he needed 13 pitches to strike out Ryan McMahon. After throwing seven consecutive fastballs to McMahon, Imanaga got him to whiff on a splitter to end the at-bat.

‘‘It’s one of those things that’s really impressive, that he just kept wanting to throw his heater,’’ catcher Yan Gomes said. ‘‘We were, like, 10 or 12 pitches in, and I was like, ‘Let’s get this over with, let’s go to the next guy.’ And he’s like, ‘No, I’m going to keep going and keep going at him.’ ’’

Imanaga didn’t issue a single walk and seemed to become more efficient as the outing continued, culminating in his strikeout of Jones to end the sixth.

‘‘It seems like he’s pretty fiery, a fiery competitor,’’ left fielder Ian Happ said. ‘‘Obviously, you don’t get that in spring training. You’re not going to be fist-pumping coming off the mound in a spring-training game. So with that atmosphere, with the crowd, to see his presence and how much he cares is pretty cool.’’

The Cubs took the lead in the sixth. Happ and Seiya Suzuki hit singles to put runners on first and second for Morel, who hit a sharp ground ball into left field. Happ held up at third, but then the ball got under Jones’ glove. Happ and Suzuki crossed the plate as Jones chased after the ball rolling at the base of the left-field wall.

Morel slowed at third as Jones finally threw the ball in, but his throw to the cutoff man was offline, and Morel turned the burners back on. He dived across home plate, hopped up and punched the air with an uppercut. And the momentum fully had shifted to the Cubs.