Sometimes, you just know "this is a tough game". And, it maybe isnt that the other team is better but they play real tough... almost over the limit-defense, maybe some hard shoving, etc. And of course, you dont want to get injured, you want to play a good game of basketball. But, at the same time, you dont want to disappoint. You dont want to disappoint your team, yourself - and you dont want to give it to your opponent by not measuring up to his or hers intense playing, even if it is over-the-top play.
These players are considered living on the edge on the defensive end.
"I just had so much aggression and so much built up and so much anger, especially because many other teams passed up on me. I just wanted to go out there and every single night just make it hard for the opponent to dribble the ball up the court—be fearless out there and do whatever it takes to try to put my team in a position to win basketball games." http://bleacherreport.com/articles/2003558-patrick-beverley-breaks-down-what-makes-him-the-peskiest-defender-in-the-nba
Patrick Beverly, guard of the Houston Rockets, is considered almost "dirty". But he is a very high defensive IQ player that can guard any backcourt and knows the passinglanes. He always is a threat to handle when the opponents go on offense.
"He’s fundamentally sound defensively and he plays harder than everybody else defensively. He has a competitive desire to compete individually. That’s very uncommon. Most defensive players I face want help all the time. I’ve never heard him ask for help. He likes taking the challenge." Kobe Bryant on Tony Allen. http://bleacherreport.com/articles/2003558-patrick-beverley-breaks-down-what-makes-him-the-peskiest-defender-in-the-nba
Tony Allen and Patrick Beverly are players who can take away another players triple-threat. Kobe Bryant giving him some notice on what Allen does best, and perhaps the best in the league doing it.
Play hard, but play smart.