Before Pratt could get into specific details for Sean Casey, Ivan Rodriguez and Brandon Inge in the third inning, Karstens interrupted his catcher. The Yankees now had much larger problems to contend with.
"Man, I'm hurting," Karstens told Pratt, pointing to his stiff right elbow.
"I've got to tell Gator [pitching coach Ron Guidry]," Pratt replied. "There's no reason to be a hero."
Karstens, 24, could have wrapped up his candidacy for the Yankees' fifth rotation spot with a solid effort on Sunday, but instead left Joker Marchant Stadium having secured an appointment on Monday in a Tampa, Fla., doctor's office.
Though Guidry said he saw nothing out of the ordinary in Karsten's pregame bullpen session, Karstens admitted he was never able to get loose. He continued to throw anyway, hoping his stiffness might evaporate by the time he reached the mound.
It never did. Karstens threw 46 pitches in a two-inning appearance, allowing six runs and six hits -- including a three-run home run to former Yankee Gary Sheffield -- before finally coming clean on his condition.
"I didn't want to push it too much and have something really [bad] happen," Karstens said.
Pratt also caught Karstens in his previous start against the Blue Jays last Monday in Dunedin, when the right-hander surrendered four runs in 4 1/3 innings -- the first rocky effort of the spring for Karstens, who opened camp with the equivalent of a complete-game shutout, striking out nine and walking none in nine innings.
"He basically had the same stuff [Sunday] he had in Dunedin," Pratt said. "I haven't really caught him when he was dealing. He couldn't make a difference. He basically didn't have the control that I've heard he has. It looked like he was forcing some pitches."
With the Yankees' preparations for the regular season nearing completion, Karstens said it would be disappointing if he learned of a setback this late in camp, but said he understood the situation.
"If I'm not 100 percent healthy, I can't really help them anyway," Karstens said. "Anytime you've got something wrong, it kind of worries you a little bit."
The injury is the second this week for the Yankees' suddenly beleaguered pitching staff, which took a major hit on Saturday when it was revealed that ace Chien-Ming Wang had been diagnosed with a Grade 1 strain of his right hamstring.
Wang is expected to be sidelined until late April at the earliest, and it was believed that Karstens would fill the void in the rotation until then.
"Obviously, he's going to be shut down for a time, which is going to muddy the waters," Yankees manager Joe Torre said.
Torre said that the team would discuss potential solutions, among other topics, in an organizational meeting on Monday. It's probable that right-hander Darrell Rasner -- who has allowed two earned runs in 12 innings this spring, compiling a 1.50 ERA -- has vaulted into serious consideration for the roster spot.
"The first concern is for [Karstens]," Torre said. "The team is obviously important, but you need to have these players taken care of, especially when they have bright futures ahead of them. Hopefully, it's not a big issue."
Karstens said that he only recalled having elbow problems once before, and it was of a dissimilar nature.
As a freshman at Mount Miguel High School in Spring Valley, Calif., Karstens suffered from bone chips in his growth plate, an injury which restricted him from everyday activities as mundane as combing his hair.
He said the sensations he felt Sunday were more of stiffness than pain. Either way, the Yankees will likely have to look elsewhere to fill their needs for the Opening Day roster.
Jason Giambi said that there is concern in the clubhouse, but stressed that the team still has time to rebound.
"I don't know if you hit the panic button," he said. "It's not like we're at the All-Star break. The biggest thing is just to take care of it and hopefully it won't be as bad."
Bryan Hoch is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.