NEW YORK — Yankees ace Chien-Ming Wang is expected to be sidelined until at least September after injuring his foot running the bases, prompting club co-chairman Hank Steinbrenner to chastise the National League for playing without a designated hitter.

An examination in New York on Monday showed Wang partially tore a tendon and sprained his right foot Sunday during the Yankees' 13-0 interleague win at Houston. He will be on crutches and wear a protective boot for a minimum of six weeks, the latest blow to the team's banged-up pitching staff.

"My only message is simple. The National League needs to join the 21st century," Steinbrenner said in Tampa, Fla. "They need to grow up and join the 21st century.

"Am I (mad) about it? Yes," Steinbrenner added. "I've got my pitchers running the bases, and one of them gets hurt. He's going to be out. I don't like that, and it's about time they address it. That was a rule from the 1800s."

Making a rare appearance on the bases at an NL park, Wang pulled up rounding third and hobbled home on Derek Jeter's single. Wang doubled over after scoring, pointed toward his right foot and was helped off the field.

"This is always a concern of American League teams when their pitchers have to run the bases and they're not used to doing it," Steinbrenner said. "It's not just us. It's everybody. It probably should be a concern for National League owners, general managers and managers."