Warren Sapp -- I'm No Deadbeat Dad!

Warren Sapp denies half of the allegations levied against him by his ex-wife -- saying he's not behind on child support, but maybe a little on the alimony ... sources close to Sapp tell TMZ.

As TMZ first reported, Sapp's ex-wife filed documents in Florida saying the former NFL star owed her $728,100 in back child support and alimony.

But sources close to Sapp tell TMZ he's current on his child support and that to Warren, his kids "always come first."

However, like we've seen with so many retired sports stars, we're told Sapp feels his alimony is too high since his playing days are over and the paychecks he gets as an analyst just don't stack up.