Burnett was struck in the face between the eye and temple when a baseball he was trying to bunt bounced off his bat during a spring training workout in Bradenton, Fla.
The 35-year-old hurler is being sent back to Pittsburgh for further examination, Pirates General Manager Neal Huntington said.
Burnett was obtained by the Bucs from the New York Yankees in a Feb. 18 trade and is expected to be the club's opening day starter.
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