Assists are good, by definition there's a goal at the end of them. So it really depends whether he's actually good at assists or its a few assists. And if you are getting enough team goals (or not) then thats what matters.

I'm sure there are a few managers who have let go players because they didn't have enough in their goals column and then saw team goals fall after the sale.....I did.

PS Just label all the things that we don't know/understand with a tag marked Performance Factor - then its just 1 unknown.