Saints star Demario Davis is going to bat for Drew Brees ... telling TMZ Sports he sees absolutely no decline in the QB's game whatsoever.

In fact, the linebacker says he believes the critics who are calling the 41-year-old washed are actually FUELING Drew to a monster season this year.

"You can see him channeling it," Davis told us of how Brees is handling the criticism.

The QB began the year not looking quite like himself -- he was checking down a lot and not exactly pushing the ball up the field at will -- and it had many wondering if Brees was done.

Things got so dicey for a while there ... some called for backup Jameis Winston to take over the starting reins in New Orleans.

But, Brees has turned things around recently -- the Saints are now proud owners of a 5-game win streak -- and Davis says he ain't surprised one bit.

"I don't know where the negative feedback be coming from," Davis says. "If people just look at the numbers, he's been as efficient this year as he's ever been."

"And when you look at somebody that's able to do that week in week out, go out there and be that efficient, if I'm putting together a roster, that's the type of quarterback that I want."

Through 8 games so far this season, Brees has 2,120 passing yards, 17 passing TDs and just 3 INTs. His QB rating is a whopping 110.3.

"He's the reason why we've had as much success as we had," Davis told us.

There's more ... Davis also spoke with us about the presidential election results -- and he even offered up a message of encouragement to Joe Biden and Kamala Harris!