The Rangers announced Darvish's injury 2½ hours before he was scheduled to face the A's. Scott Feldman started in his place, giving up two runs on four hits and three walks in four innings. Feldman was removed after allowing a leadoff single to George Kottaras in the fifth. The right-hander allowed two runs and four hits in four-plus innings before being relieved by Michael Kirkman. The Rangers lost 3-2 in 10 innings.
"I woke up with a stiff neck," Darvish said in a statement. "I really wanted to throw tonight, it's just unfortunate I can't. I'm continuing to have treatment and am taking the situation day-to-day."
The Rangers said Darvish felt the stiffness on Tuesday morning, came in for treatment and still had stiffness. The date of his next start is still to be determined.
Manager Ron Washington said he doesn't believe the stiffness is serious and that the club will take it day by day.
"He was disappointed he wasn't going to start and we're disappointed he's not going to start," Washington said.
Washington said Darvish called the club on Tuesday morning to let them know and then came in and tried to throw some pitches, but wasn't able to do it at full strength.
Darvish, who is 16-9 with a 3.90 ERA, has four consecutive outings of at least seven innings and four or fewer hits allowed and is just the third Rangers pitcher with such a streak (joins Gaylord Perry and Nolan Ryan who did it four straight times). His 16 wins are the most for a big league rookie since Ivan Nova won 16 in 2006.
The 26-year-old Darvish has 214 strikeouts through his first 28 career starts. He reached the 200-plateau in his 27th start, the fourth-fastest to reach 200 strikeouts since 1918 and the only pitchers to do it in fewer games: Kerry Wood (23), Hideo Nomo (23), Dwight Gooden (25), and Mark Prior (27). Darvish also has 88 walks, third-most in the American League.
Darvish has been healthy most of the year. He did skip a start in late August with a tight right quadriceps, but has reeled off seven straight quality starts -- five of them wins.
Feldman, 29, made his 21st start of the season. He was moved from the rotation to the bullpen when Martin Perez was called up to make a start last week. Feldman entered Tuesday 6-11 with a 5.19 ERA and had lost his last five decisions when starting. He did pitch three scoreless innings of relief on Friday in Seattle.
The first-place Rangers entered Tuesday with a five-game lead over the Athletics.
Information from The Associated Press was used in this report.