“The sideline is a defender’s (best) friend” is a football saying. “The baseline is a defender’s (best) friend” is a saying in basketball and tennis. If a football cornerback can pin a wide receiver to the sideline, that wide receiver has less room to catch the ball and run. If a basketball defender can pin an offensive player against the baseline, the offensive player has limited space to move. The sideline or baseline acts like an extra defender.
 
“That baseline is the defender’s friend and the offensive player cannot cross that line without loosing possession of the ball” was cited in a 2000 basketball post. “l’ve always said that the sideline is a defender’s best friend—it’s never missed a tackle yet” was written in a 2011 football book by Ron Jaworski.
 
 
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Houston win
slong
11/23/00
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A cardinal rule of defense is to give your opponent the lowest percentage shot possible. Last on defense but not least we need to cut off that baseline.  Houston got alot of penetration around the baseline and so did Philly.  That baseline is the defender’s friend and the offensive player cannot cross that line without loosing possession of the ball.  We need to use this fact and force defenders into the middle where our other defenders can help out.
   
GU Board Forums—Basketball discussion
Defense Fundamental Question
MDABE80
01-20-2009, 09:21 PM
Not much has changed except the athleticism. The basleine is the defender’s friend. Best to guard it..it’s like a 6th man if used right. The kids these days are so quick to the middle though, it’s hard to clog lanes unless the defender’s feet move and quickly. Team defense will do that..like Midwest indicated.
 
Google Books
The Games That Changed the Game:
The Evolution of the NFL in Seven Sundays
By Ron Jaworski
New York, NY: ESPN Books
2011
Pg. 205:
That meant the sideline was now a long way away, opening the passing game even more. l’ve always said that the sideline is a defender’s best friend—it’s never missed a tackle yet.
 
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the baseline is a defender’s best friend
5:35 PM - 27 Mar 2011
 
CSN Mid-Atlantic (sports)
HALL WILL MISS AN OLD FRIEND IF HE PLAYS SLOT
June 08, 2012 2:21 PM
They say that the sideline is a defenders best friend. Old Man Sideline never missed a tackle or blew a coverage.DeAngelo Hall could be missing his best friend a lot this season.
     
BluegrassPreps.com
Why does the NFL insist on two feet inbounds on catches?   
CincySportsFan 
Nov 26, 13, 11:40 AM
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For the majority of the game, the sideline is usually the defender’s friend…but, when it gets down to crunch time, suddenly it’s their enemy?
 
GoalGetters U11
Tuesday, May 3, 2016
One-on-One Defending 101
Posted by Don Seiler at 12:03 AM
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What we want to do is pressure and contain the attack, slowing them down and forcing them to one side away from the goal. Remember, the sideline is a defender’s teammate. If you can direct an attack toward the side and contain it, there’s a good chance the ball will be turned over out of bounds.
 
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The Return Of E.J. Gaines
By QBKlass and misone on May 25, 2016, 11:39a
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Misone: And Gaines used the boundary as an extra defender and forces Fitzgerald to the sideline. As the old saying goes, “The sideline is a defender’s best friend.”