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Anthony Richardson 's season is off to a rough start ... 'cause he was removed from a preseason game after a tackle left his finger twisted to a nasty angle.

The Indianapolis Colts QB and his squad were facing off with the Baltimore Ravens Thursday when halfway through the first quarter linebacker David Ojabo sacked the two-year NFL vet.

While it looks like an average hard hit on the gridiron, Richardson was lifted from the game shortly after this tackle ... and, when you see his finger, it's clear why. Gallery Launch Gallery NFL

Click at your own risk ... the pinkie finger on his right hand is bent at nearly a 45-degree angle to the right, away from the rest of his digits.

It certainly doesn't look good ... but, we don't know how severe the injury is yet -- could be

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