He felt it first while letting go of a pitch in a simulated game. Yates threw a few more, trying to will away the discomfort, but with no success.
Yates threw long toss the next day, but the elbow still hurt. He tried throwing again, but the pain only augmented.
A trip to Dr. James Andrews followed, and the diagnosis was devastating. Inflammation in Yates' surgically-repaired elbow meant that he had to halt his rehab program. Those chances of being back in the big leagues after the All-Star break were replaced with the crushing truth that Yates might never pitch on that stage again.
So, he called home.
"I thought I was done," Yates said, revisiting the hour-long conversation with his dad. "I asked him if there was any work that I could do back there. I was ready to try and figure out what I could do next."
Yates had already considered his options. He looked into being a firefighter. The flexibility of the job -- two days on, three days off -- was appealing for a native Hawaiian, who wanted to leave time open for surfing. He thought about pursuing a career as an emergency medical technician.
Neither career would be ideal. But the reality of his situation had become clear -- there had to be a backup plan.
"I wasn't ready to quit," Yates said. "But I thought that I may not have any other choice. You start looking at things differently when you question whether you can do this anymore. I have a family, and I have to make ends meet. Those are the things that you start thinking about when you wonder if you'll ever pitch again."
Gary Yates listened as needed and then stepped in with his own advice. He told his son to consider how much he loved playing baseball and asked him if he was truly ready to give it up. Gary encouraged his son to give it one more shot.
"So," Yates said, "I stuck with it."
The perseverance has paid off. Yates arrived in Bradenton, Fla., in January and has been throwing under supervision since.
All reports are overwhelmingly encouraging. In fact, if there is a negative to cite, it's that Yates is too fired up to get back on the mound.
"He is so far ahead of everybody else, it's unbelievable," pitching coach Ray Searage said this week. "It looks like he can pitch tomorrow. Sometimes I have to yank that chain on his neck and say, 'Relax.' He's trying to make up for time that he lost. No. Live for the moment. Don't think about having to make up for stuff that happened in the past. That's over with."
Yates, who is very much in the mix for one of the team's bullpen openings, is eager to see how his elbow responds once he's tested not in supervised side sessions, but in actual exhibition games. He plans to increase his usual Spring Training workload from about nine innings -- the number he's typically logged in the past -- to closer to 15.
It will be a sort of litmus test for Yates, who has made just 15 relief appearances since the end of the 2008 season.
"I'm looking for consistency and crispness in my pitches more than anything," Yates said. "By the end of the spring, I'll need to make sure that I can pitch on back-to-back days. There are small steps like that."
Yates has been told that his velocity has ticked back up, near where it used to be. That's not so much a concern as making sure the command returns in full. Hitting the corners of the plate at 94 mph will be more effective than throwing it down the middle at 97. If he can reestablish both command and velocity, that's a bonus.
The right-hander has set his goals as if he knows he will soon complete the journey back. He talks about the need to avoid that handful of big innings that inflate his ERA every year. Yates wants to work his way back into a setup role, and he eyes eventually reestablishing himself as a leader in the Pirates' bullpen.
And, in doing so, Yates would reward his father for his insistence that he give it one last try.
"Tyler is looking good right now," Searage said. "I'm pulling for him. I wish him all the luck in the world."