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Kirk Cousins deserves Matt Stafford money ... because he's BETTER than Matt Stafford -- so says Joe Theismann.

Cousins has been tearing it up this year ... and is coming off a 42-24 dismantling of the Green Bay Packers where he once again went H.A.M. ... throwing for over 375 yards and 3 TDs.

Kirk is currently playing under the franchise tag earning $20 mil for this year ... but when we talked to Thiesmann he says it's time for Kirk to get a major upgrade in the coin dept.

"If he can stay healthy, you're talking about a $100 MILLION dollar contract."

Joe's metric? He says there are a lot of other franchise QBs making the century mark ... and he feels Kirk is better than A LOT of them.

"I think he's better than a Matthew Stafford, I think he's better than Joe Flacco, I think he's better than Jay Cutler."