If you get paid great, you better play great. That’s the law of the NFL salary cap jungle and that’s the reason why Corey Webster remains on the Giants roster, but at a severely reduced salary. Webster is coming off a sub-par season and was scheduled to make $7 million in base salary in 2013. It was an unhealthy combination that wasn’t going to be allowed to exist. Webster has agreed to a pay cut, slashing his 2013 salary to $4 million, which saves the Giants $3 million on the salary cap as Webster enters the final year of a $44 million contract he signed in 2008. If Webster had not agreed to the change he would have been cut. He’s been a starter on both of the Giants’ Super Bowl-winning teams since 2007 and now gets a chance to prove, at 31 years old, he’s not on the downside of his career. Asked on Tuesday if he thought Webster and right tackle David Diehl — another high-priced veteran coming off a rough season — were worth keeping around, Tom Coughlin said “I think there’s no doubt they can definitely help the team. I do want them back. They can still contribute.’’