Darvish is dealing with stiffness in his neck, but the examination showed no structural damage. He will resume a throwing program on Saturday and the Rangers will map out a plan from there.
"We're making sure we handle this responsibly on the front end so we don't put him in harm's way," assistant general manager Thad Levine said.
Tommy Hanson will not be in the rotation. The Rangers released him on Wednesday morning. They wanted Hanson to keep pitching in Triple-A, but Hanson instead preferred to take his release and look for a Major League job. The Rangers have signed veteran pitcher Scott Baker to a Minor League contract to reinforce their Triple-A Round Rock rotation.
Martinez is in the rotation because the Rangers wanted to keep Alexi Ogando in the bullpen.
"Alexi has been successful in every role," general manager Jon Daniels said. "But this is how the team sets up best overall."
Martinez was not in big league camp, but he has risen quickly through the Rangers' system after being taken in the 18th round of the 2011 First-Year Player Draft out of Fordham University. He was 12-7 with a 2.50 ERA in 25 starts and two relief appearances last season between Class A Myrtle Beach and Double-A Frisco. Martinez was 2-0 with a 1.13 ERA in five games at Frisco. He pitched two scoreless innings against the Indians on Tuesday.
"He's had a very good camp," Daniels said. "He has impressed in his limited time up here. He has three solid pitches -- four, really -- tremendous makeup, athletic, fields his position. He's poised and attacks the strike zone. Obviously he's here quicker than anticipated, but if you look at our injuries, we had the most confidence in Nick."
Scheppers came to camp hoping to win a spot in the rotation, and he'll leave Arizona as the Opening Day starter after posting a 3.07 ERA with a 1.02 WHIP and a .208 batting average in four games. He will be on the mound when the Rangers face the Phillies at 1:05 p.m. CT Monday in Arlington.
"He has been profiled as a No. 1 guy," manager Ron Washington said. "I feel with the innings he got for us last year late in games under pressure, he'll be able to handle Opening Day well. I like the way he has been throwing the ball."
Scheppers has pitched in 118 Major League games, but this will be his first start. The last pitcher to make his first Major League start on Opening Day was Fernando Valenzuela for the Dodgers in 1981.
"I'm just extremely excited for the opportunity," Scheppers said. "Let's get this season started and get things rolling in the right direction."
Scheppers will be followed by Perez and Ross against the Phillies. Saunders will make his first start on April 4 against the Rays, followed by Martinez on April 5. Saunders has made 221 Major League starts and Perez has made 26. The other three will be making their first Major League starts.
The rotation likely will not stay intact long. Darvish, Matt Harrison and Colby Lewis could all be options by May. Baker gives them depth at Triple-A. He was released by the Mariners this week but has made 162 Major League starts, mostly with the Twins from 2005-11.