Someone bet $3.1 million on the Eagles to beat the Panthers

"it pushed Panthers odds to +650." article says, without saying where those odds started from, so what do we know?

we know that +650 doesn't make a previously made -700 bet "upside down" exploitable, as Unjon puts it*

does it make it possibly +EV assuming the oddsmaker has the probability right? I did doubt it since it isn't upside down vis a vis original, but checking today's NFL games with a calculator. looks like the moneyline bets like to be put at about 5% vig. So a -700 should have been countered with about +475

the implied probabilty if fair odds are 1/8 and 1/5.75, resp., naturally not the same. But we can estimate the oddsmaker thought the probabilty of the underdog winning was in the middle , about 1 in 7. So if the oddsmaker was accurate, a fair bet for that +zone moneyline would be 6 to one, or +600. +650 then is +EV with all those assumptions in place.

conclusion: if you know the odds move due to a big bet, not player injury or similar, then a +EV situation may be in place.

Disclaimer: mistakes possible, no one checks this work

* just giving often helpful Unjon credit for pointing out that this can be determined at a glance