Right-hander Taijuan Walker is out for the season after undergoing Tommy John surgery.
Ray, an All-Star and 15-game winner last season, left with one out in the second inning of Arizona's 3-1 loss at Washington on Sunday. Diamondbacks manager Torey Lovullo said there is no timetable for his return.
"He's a little bit frustrated because he thought he was finally throwing the ball the way he wanted to yesterday and we were all noticing that,'' Lovullo said, "and this jumps up and grabs you.''
Lovullo wasn't ready to say who would take Ray's next scheduled start on Friday, at home in the opener of a three-game series against World Series champion Houston.
Ray is 2-0 with a 4.88 ERA and 48 strikeouts in four starts this season.
To take Ray's roster spot, the Diamondbacks recalled right-handed reliever Silvino Bracho from Triple-A Reno.
Lovullo called it ``a huge test'' to lose two-fifths of the starting rotation before the end of April.
"That's what a baseball season is for me,'' Lovullo said.
"It's a series of tests that when you stick together, you group up as one, support your family, you get through these tests.''
Matt Koch, up from Reno, has made two starts in place of Walker and is 1-0 with a 1.93 ERA.