When God saves someone, He saves them real good.  It is a radical transformation from death to life from sin to salvation.  He changes us from the inside out and in Scripture when the Lord works we are born again.  Paul's change was surely radical, he went from wanting to kill Christians and hating Jesus Christ to loving them and their Savior, only the Lord can do that.  It is the sovereign power of God at work to show such grace to someone that didn't even want Jesus Christ.  God used an unknown servant named Ananias to come help Paul and be sure that he was discipled.  A short time later Paul went from preaching hate for Christ to preaching the Gospel of Christ.