Defour, huh?
Might be worth the gamble, but he's going to be quite expensive.
He can play both as a holding midfielder (mostly does that these days), but also as a typical box to box or even attacking mid, and is pretty good in all these roles. So that's definitely a plus in my book. Pretty decent shot as well, high workrate, decent attitude.
On the other hand, he's always getting (different) injuries (could just be bad luck, but still) & that has seriously hampered his growth as a player. He's, obviously, often compared to Witsel, but unlike Witsel, Defour really hasn't made any progress the last 2 seasons. He's also not the "smartest" player, in terms of wasting a lot of unnecessary energy or positioning (at times). Shouldn't be too difficult too improve this side of his game though.
Right now, I don't think Defour would be an immediate upgrade for our midfield. But the potential is definitely there and just the change in scenery & the chance to compete in a more competitive team/league, could very well mean that it won't take too long (as in only a few months) for him to earn his spot.
Someone asked if the gap between both leagues wouldn't be too big, but that's difficult to say. Both Vandenborre & (especially) Onyewu were regarded as some of the best players in the Belgian league when they left for Italy, yet both failed miserably. But that obviously doesn't mean that the same would happen to Defour.