"Stretching reduces the strength-endurance capability of a pitcher (Kokkonen, Nelson, & Arnall, 2001).
Excessive stretching in warm-ups inhibits strength performance (Kokkonen & Nelson, 1996) and force production (Behm, Button, & Butt, 2001; Evetovich, Nauman, Conley, & Todd, 2003; Fry, McLellan, Weiss, & Rosato, 2003).
Stretching routines should be moderate to minimal and cease at least one hour before the game (Fowles & Sale, 1997).
Stretching reduces throwing velocity (Noffal, Knudson, & Brown, 2004).
Stretching does not prevent injuries (Herbert & Gabriel, 2002; Wilkinson & Williams, 2003).
Some researchers have said that no stretching should be performed at all before explosive activities (Young & Behm, 2003)."
Yes, indeed I have heard of this. And it's not just for pitchers.