SANTA CLARA — Coach Jim Harbaugh had no trouble reporting Wednesday to 49ers practice, a day after his wife, Sarah, gave birth to their first son, Jack.

“Jack Jr. will understand in 20 years,” Harbaugh said. “He wants to win, too.”

Harbaugh commended his wife on a “great job,” adding that she deserved a “gold medal for timing.” The couple’s third child came 10 days early, and Harbaugh wasn’t planning on skipping Sunday’s regular-season opener at Green Bay.

“My wife would have understood, too. She wants us to win and it was great to be there for the birth,” Harbaugh said. “Wild horses couldn’t have dragged us away from this game coming up this Sunday.”

The newest Harbaugh is named after his grandfather, Jack, who coached football for 43 years and led the Western Kentucky Hilltoppers to the Division I-AA national championship in 2002.

“Everything’s scary good,” Harbaugh added. “Word’s out. Jack Jr. reported for duty yesterday at 1:27 p.m. He was 8 pounds, 8 ounces. He came 10 days early, which is to be expected. The good ones like to come in early.

“Also I think it bodes well for the 49ers. It’s a sign of good luck to come, perhaps — Jack Jr. being born on the fourth day of the ninth month of this year.”

It is the elder Jack Harbaugh that long ago coined what became the 49ers’ post-win catchprase throughout Jim Harbaugh’s first season as coach last year: “Who’s got it better than us? Noooo-body!”

This is the Harbaugh’s third child, and Jack has already gotten to meet his older sisters, Addison and Katherine. Harbaugh also has three children from a previous marriage: Jay, James Jr. and Grace.

About 15 minutes before Tuesday’s team picture, a frantic and smiling Jim Harbaugh did a curious lap around the locker room, saying farewell to his players and shaking their hands. A team spokesman explained that Sarah Harbaugh had gone into labor and asked that the matter be kept private.

Running back Frank Gore was being interviewed when Harbaugh rushed up to him and said: “Frankie … boom … gotta go.” To which Gore replied: “Huh? What did he just say?” Informed of the impending birth, Gore made sure to shake Harbaugh’s hand and wish him well as the coach dashed off to the delivery room.

Two hours later, baby Jack Harbaugh checked in at 21 inches. Gore’s jersey number: 21.

“He looks pretty big. He probably would have been a 10 pounder,” said Harbaugh, noting his son can grow up to play any position, or, better yet, multiple positions.

First with the birth announcement was CSN Bay Area’s Dave Feldman, Harbaugh’s long-time friend and Palo Alto High School basketball teammate.

Exactly nine months earlier, the 49ers clinched the NFC West title with a 26-0 victory over the St. Louis Rams.

Who’s got it better? Aaaa-baby. Named Jack.