Pitcher Rubby De La Rosa is ‘very surprised’ to be in the major leagues

Reporting from Houston — Having promoted Jerry Sands to great fanfare last month, the Dodgers dipped into the minor leagues again Tuesday for another top prospect.

Consider Rubby De La Rosa as shocked as anyone by his arrival in the major leagues.

“I’m very surprised,” said the 22-year-old right-hander who had been pitching for double-A Chattanooga fewer than 24 hours earlier.

Manager Don Mattingly said the Dodgers “wanted to put another quality arm out there” with four relievers on the disabled list and other pitchers battling bouts of ineffectiveness.

Though he had been used exclusively as a starter this season, De La Rosa is expected to make his major league debut as a reliever. But Mattingly said the Dodgers envision the native of the Dominican Republic as a starter over the long term.

De La Rosa, who went 2-2 with a 2.93 earned-run average this season in eight starts with Chattanooga, features a fastball that has been clocked in the upper 90s, complemented by an improving slider and a changeup that Mattingly described as “dirty.” He had 52 strikeouts and only 19 walks in 40 innings.

“When you see his stuff,” Mattingly said, “you think this guy’s a big-league pitcher.”

The Dodgers designated reliever Lance Cormier for assignment to make room for De La Rosa on their roster. The seldom-used Cormier went 0-1 with a 9.88 earned-run average and had made only five appearances since April 15.

When the Dodgers broke camp in spring training, they gave their reigning minor league pitcher of the year no indication he would pitch in the majors this season.

“They told me to keep working hard, and that’s it,” De La Rosa said.

De La Rosa was informed of his promotion Monday night in Zebulon, N.C. He said he informed an aunt and uncle of his promotion and that his late grandmother would have been proud.

“I wanted to do it for her,” he said.

Short-handed again

The Dodgers started a second consecutive game without right fielder Andre Ethier or catcher Rod Barajas in the lineup, though the duo could return as soon as Wednesday.

With the Astros starting left-hander J.A. Happ, Mattingly said it was a good opportunity to give the left-handed-hitting Ethier a day off.

“I need him to be able to go 100%,” Mattingly said. “Last year he got banged up and he was hobbling around the whole time out there the second half of the year. I just don’t want to see that.”

A day after saying he did not feel overly sore after his collision with an outfield fence Sunday, Ethier did not want to further discuss his injuries.

“I don’t need you to check on me,” he told a reporter inquiring about how he felt. “We have trainers to do that.”

The 100 club

Matt Kemp became the fourth-youngest player in Dodgers history to hit 100 career home runs Monday at 26 years and 242 days.

But the feat required 675 games and 2,673 plate appearances over parts of six seasons, a pace he would like to accelerate.

“One hundred took me a while,” Kemp said. “We’ll see if I can hit 100 more in less time.”

ben.bolch@latimes.com