Instead, an MRI exam late Friday revealed just about the worst news possible.
Darvish has partially torn ligaments in addition to inflammation in his troublesome right elbow, and might need Tommy John surgery. It's another massive blow a suddenly snake-bit franchise that struggled through a rash of devastating injuries last season.
"Not going to sugarcoat it, it's not the news that we wanted," Rangers general manager Jon Daniels said. "You basically have two choices: You can hang your head and kind of dwell on it or you can do everything you can to get him the right care and get him back."
Just exactly what care that is had yet to be determined.
Darvish could try to pitch through the injury, rest it for six weeks and then try to rebuild his stamina, or undergo surgery that would end his season before it begins.
That decision will be made after he visits Dr. David Altchek, the Mets' team physician and an expert in Tommy John surgery, on Tuesday in New York.
"The concern with the first two options is, are you delaying the inevitable?" he said. "It's not black and white. ... There's no guarantees with any course."
Darvish was shut down for the final seven weeks last season with inflammation in the same elbow. He underwent an MRI exam around Thanksgiving that came back clean, and had not experienced any trouble in workouts and bullpen sessions.
He first felt tightness while warming up in the bullpen before Thursday's game against Kansas City, but did not inform anyone before taking the mound. He threw 12 pitches in his only inning, and then informed the Rangers staff of some pain.
Still, he said afterward through a translator that he did not think it was serious.
"I will be disappointed if I have to miss this season, but I want to look at all the options including getting a second opinion before I make a final decision," Darvish said in a statement Saturday. "My heart is with my teammates and our focus remains on accomplishing our goals."
Darvish will remain at camp while a second surgeon studies the MRI exam results. If surgery is required, it would likely happen in the next couple of weeks.
That could give Darvish enough time to fully recover before the start of next season.
"Given the news, he's handled it extremely well," Daniels said. "He's very pragmatic about it. He's talking to the people he's close to before making a decision."
The news is a significant blow to the Rangers, who already are minus prized young infielder Jurickson Profar. He missed last year with a shoulder injury, and recently had shoulder surgery again that might sideline him for the season.
Texas went through a devastating series of injuries last year, too. In the starting rotation alone, it lost Tanner Scheppers, Matt Harrison and Martin Perez to injuries by the middle of May. They also lost lineup mainstays Prince Fielder, Mitch Moreland and Shin-Soo Choo for long periods of time.
Ultimately, the club set a record for most players on a 25-man roster in a single season, and needed 40 pitchers to get through 162 games -- three of them position players. The rotation alone required 14 different pitchers, nobody making more than 25 starts.
Darvish was limited to 22 starts between neck stiffness that caused him to miss the beginning of the season the elbow inflammation that caused him to be shut down late in the season.
"I'm personally not taking the position, Here we go again," Daniels said. "Any time you have an injury there is risk for recurrence down the line. What we're seeing is effectively an extension of what he dealt with last summer, at a significantly more severe level."
Darvish was still effective when he was on the mound last season, going 10-7 with a 3.20 ERA. But he seemed to lack the same kind of life on his pitches that he had his first two years, when he was in the running for rookie of the year and then logged more than 200 innings.
"I feel bad for him. I have empathy for him," first-year Rangers manager Jeff Banister said. "No doubt, there's some feeling there. You never feel good about any athlete in any sport that has some obstacles that they need to overcome."
The Rangers already had one spot up for grabs in the rotation. Now, a group that includes Ross Detwiler, Nick Tepesch, Chi-Chi Gonzalez and Anthony Ranaudo is vying for two.
"It's obviously a bad hop," Banister said, "but also, through every obstacle there's an opportunity. Let's never lose sight of that."
Darvish Mulling Tommy John Surgery
ESPN injury analyst Stephania Bell discusses Rangers pitcher Yu Darvish's sprained ligament in his pitching elbow and possible treatment options.
Darvish Injury Devastating For Rangers
Tim Kurkjian explains how significant the loss of starting pitcher Yu Darvish is to the Rangers' season.
Darvish's MRI Reveals Sprain In Elbow
ESPN.com senior writer Jerry Crasnick discusses the news that Rangers ace Yu Darvish has a sprained ligament in his pitching elbow and how Texas could try to replace Darvish at the top of its rotation.