Cecilio is grimacing because he has just thrown off his hand. You can just make out the mangled nub and a haze of shattered hand innards.
Impressively, Guante pitched for another 6 seasons after this horrific injury. He was a slightly above average pitcher for 9 seasons and paved the way for handless pitcher, Jim Abbott.
The Yankees traded Doug Drabek for Guante in 1987. They also traded JT Snow for Abbott in 1992. If Johan Santana was missing a few digits, the Yankees may have pulled the trigger on a deal with the Twins!