"Collins came in after the game and told Nick that he's had some stiffness and some soreness in his elbow," manager Ned Yost said. "They gave him an MRI today and there's some inflammation in his elbow so we're going to shut him down for five or five days and go from there."
Both Collins and Bueno will have to be out at least 15 days.
"Bueno's got a sprained finger," Yost said. "He reached out on a ball yesterday that Omar [Infante] ended up catching but he sprained his pinkie finger on his throwing hand. It makes it very difficult to grip a baseball. It's probably a five- or six-day injury but it's too tough early in the season to go short in the pen."
Collins has had two rough outings. In the season's second game at Detroit, he issued two walks and gave up an RBI single in the 10th inning to take a 2-1 loss. On Sunday, he also dealt out two walks and a single and was charged with three runs, puffing his ERA to an unsightly 36.00.
"I knew something wasn't right. His velocity was down," Yost said. "He's always struggled to command his fastball but has always been able to work around it and command his secondary pitches but he was struggling to do that so I had a sense something wasn't quite right."
Yost reported that the MRI was "clean" and showed only minor inflammation.
Bueno also appeared in two games. In the home opener against the White Sox, he was charged with an unearned run. On Sunday, he gave up an RBI double and the two-run single which injured his finger.
Left-hander Donnie Joseph and right-hander Michael Mariot were called up from Triple-A Omaha.
Dick Kaegel is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.