Fan blade pretty much exploded while i was...

Fan blade pretty much exploded while i was driving the other day. Do i need to replace the fan clutch as well? I don't want to buy a new blade and have the same thing happen because the clutch is bad as well. Also, what would have caused it to break? I had noticed at idle RMP's (before the fan blade assembly broke) it would idle rough. I thought it needed a tune up, so i replaced the spark plugs, air filter etc. Still idled rough. Could it have been the fan blade was loose? when driving the vibration went away. thanks