The White Sox have already traded veteran ace starting pitcher Chris Sale, to the Boston Red Sox for four prospects.

The White Sox are also shopping No. 2 starter Jose Quintana, with the Houston Astros a possible destination.

As the Sox launch a roster rebuild, they want to avoid rushing new starters Lucas Giolito, Reynaldo Lopez and Michael Kopech to the majors.

That’s a big reason why the White Sox signed veteran Derek Holland to a one-year, $6 million contract on Wednesday.

“Derek gives us a veteran, left-handed presence for our starting rotation with a proven track record of pitching well in big games,” Sox general manager Rick Hahn said. “This move provides us with additional depth and flexibility in the rotation.”

Holland, 30, has been injury-prone the last three years while pitching for the Texas Rangers. He was limited to 20 starts last season due to left shoulder inflammation and went 7-9 with a 4.95 ERA.

If he can stay healthy, Holland can help his own future and also help the White Sox transition to a younger starting rotation.

“You never know what’s going to lie ahead,” Holland said. “I could go out there and have an unbelievable year and end up staying with Chicago and end up being a part of the process and what they’re trying to do.

“I know there’s a strong group of guys there already. I’ve talked to a few of them, and I know that their mindset is to win. Obviously, they got rid of a few pieces, but the main thing is you’ve got to turn the page and train for what lies ahead.”

In eight major-league seasons, all with the Rangers, Holland is 62-50 with a 4.35 ERA. From 2011-13, he ranked among American League leaders in complete games (6), winning percentage (.644), wins (38), starts (92) and innings pitched (586?).

Holland’s best season came in 2011, when he went 16-5 with a 3.95 ERA.

After stumbling last season while missing over two months with the shoulder issue, Holland is looking forward to working with longtime Sox pitching coach Don Cooper.

“Seeing Cooper has had a lot of success with some left-handers and getting them back to where they need to be and helping them be successful played a huge role in my decision,” he said.

Holland had an $11 million club option for 2017 but Texas exercised its $1.5 million buyout to make the pitcher a free agent.

To clear a roster spot for Holland, the White Sox designated Matt Purke for assignment. In 12 relief appearances with the Sox last season, the left-hander was 0-1 with a 5.50 ERA.