If the game is protected, maybe it's just only CD-Check or Oversize, I don't remember any game protected with unreadable sectors based protections (SafeDisc, LasekLok) were the main executable was compressed, also in safedisc protections there's always some 00000001.tmp files on the root of the disc, sometimes theres a secdrv.sys file, and some 0000XXXX.XXX files where XXXX are numbers, also when you try to dump the game, the dumping program start to report unreadable sector on the first 2-3% of the disc.
On laserlok the dumping program reports a consecutive area of mass destruction (unreadable sectors) corresponding to some kind of ring pressed on the disc.
On protections bases on sub-channel data, like SecureROM, at least in the newest one, there's always one unreadable sector and the end of the disc, and again I haven't seen any game with securom and main executable compressed.
Almost all other protections are beated with a full raw copy (2352 bytes per sector) and it will be OK.
PS. The definitive way to know is to try the game running from a copy 