BOSTON — Chris Sale understands it’s a perfect time for the Boston Red Sox to be cautious with his troublesome shoulder. He’s just frustrated that he’s back on the disabled list. Boston returned the ace lefty to the 10-day disabled list Saturday after just one healthy start. He was already on the DL earlier this month with what the team called mild shoulder inflammation. Last Sunday, he was activated against the Baltimore Orioles and struck out 12 in five shutout innings, which extended his scoreless innings streak to 28.