I would trade half of the guys on our roster for Coop, he was a huge playmaker, and for every blown coverage he gave us 3 TFLs. Not to mention the lynch mob attitude. But he was far from a complete safety, as excellent as he was at the LOS, he sucked just as hard dropping back.
Cooper was bad in coverage, period. And when he was in position to make a play, he always dropped the INT.
Trent Smith was no superior athlete. The guy has caught 3 NFL passes. Is this the image of a killer TE?

It's also not as easy as saying Coop should have never been in a scheme that had him 1:1 with a TE. LBs cover TEs on MANY plays. If you always have to provide Cooper help with the TE in any passing situation, our attacking defense all of a sudden is a lot less attacking. Are you going to put Carter and/or Tyler out there with no FS just because Coop can't cover the TE? If you're not going to use another DB, you just lost numerical superiority in the pass rush. Bob Stoops covered TEs 1:1 as DC when he was there, and no one complained.