Help with offseason for football

I’m going in to my junior season in high school and need some help with a program for summer.
I play de and have good strength-465 squat, 315 bench- but need help with quickness. My 40 time is a 4.78 but I’m still abit slow off the ball and lack great agility. Would just plyos and short sprints help, or should I add in something else?

Would increasing my flexibility help agility as well?

plyos and short sprints are good tools to include in your training- I would also suggest adding a dynamic effort squat and bench days into your lifting program. take approximately 50-60% of your max and do 8-12 sets of 2 or 3 reps. Lift the weight with perfect form and good speed up- controlled descent- 45s rest in between. short sprints of 10, 20, 30 yards with full recoveries, and high quality plyos with good rest between sets will help. remember if you don’t mind the rest intervals and keep volume low and quality high- it will be conditioning and not speed training.
we use bands, and reverse bands with high schoolers and see good explosive development, too. train for speed at least 2 days a week- before you lift if you do both the same day. Your weights are pretty nice for HS, work the speed!!

When doing dynamic box squats, is the eccentric phase fast also? And do you still pause on the box?

should be fast but dont bounce or flop on the box and u should pause on the box.

My advice-

For your “agility”, you will need to learn to control your body better. As a high school athlete, you are still in the “window” (barely) to learn and master new motor skills…In my opinion, the ability to decel your body and get it moving where you want it go makes all the difference.
You could start with videos/DVD’s if you like. My personal favorite is the Parisi videos on deceleration and agility training, but I’m sure there are others out there. If DVD’s aren’t your thing, try and find a competent coach…

“I’m still abit slow off the ball and lack great agility.”

The people on this web site (CF’s) have tremendous resources regarding acceleration out of your stance. Linear speed mechanics are needed here. But when it comes time to change direction and react, - this is where a great deal of training is needed!

Good luck

Man you just need to do agility drills(makes you athletics, which it seems is your problem), those are the easiest to build, the speed will be the hard part but there is hope, agility drills will work your quickness hence your explosion off the ball. So do the speed stuff and the other stuff the other fellas mentioned just add in agility stuffs, like L cone drills and short shuttle type stuff i’m sure you can find other agility drills on the web or in your library.