Roger Clemens had a reputation for being a 'head-hunter' due to incidents during this interleague game in 2000. Photo is credited to ESPN
The fact that Roger Clemens and Mike Piazza are two of the greatest players in MLB history make this match up worth the price of admission. Piazza previously had Clemens' number and hit multiple home runs off him in the previous year's match up.
It is no secret Clemens let his emotions get the best of him during the heat of the battle. This was no different.
Clemens, usually noted for his remarkable command, unleashed a high fastball which struck Piazza in the head. The All-Star catcher lied on the ground for several minutes motionless.
Piazza was diagnosed with a concussion and missed the Summer Classic in Turner Field.
The boiling point between the two was actually during the Subway Series when Clemens managed to pull off one of the most mind-boggling and dangerous acts on a baseball field.
The steroid allegations which have occurred in recent years have not helped his reputation, and perhaps explains his erratic behavior at times.