The Kiwi back five player who joined the Blues in the summer has fractured his sesamoid, a small bone beneath the big toe, and has been ruled out for up to three weeks.
That means the 25-year-old will miss the Magners League clash with Aironi Rugby on Friday and the last two rounds of European action.
"After the Northampton game I had a scan and it showed a fracture of the sesamoid. I have no idea when I did it, it could have been a pressure thing at the scrum, or in a tackle, I just don't know," said Paterson.
"It's just a case of resting up and letting it heal by itself. Obviously that means I'm restricted training wise but I'm keeping busy in the gym and doing a lot of work in the pool.
"I'm ruled out but this game is of huge importance to us. Hopefully we can bounce on from the win last weekend and play the way we did in the first half. In the second half we fell off for a bit so it's vital that we get back to that first-half performance.
"We can't underestimate them and we will worry about the win first - if we can get the bonus-point then that's a plus."
Paterson admits he is loving every minute of life in Cardiff and he is eager to get back on the pitch to help the Blues during the Six Nations.
"It's been a change of lifestyle in a new part of the world and Cardiff is a great place," added Paterson.
"The club is the main thing for me. They have all the facilities and infrastructure to be a winning team.
"Each game is as important as the next at the moment. We have top players and it's just a case of making sure we do the right thing at the right time.
"We have got our game plan that we have implemented over the past months. We're making opportunities - it's just about realising when and what to do with the ball. We have to look after the ball better if we are going to win games.
"The next few months will be big. Obviously we will lose a lot of players like we did in the autumn. We'll really have to rely on the squad depth to do the business on the park.
"But whoever pulls on the jersey has to carry on with our game-plan, that is key. There's still a lot of water to go under the bridge this season but we want to keep pushing."
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