Did the Fathers Know the Gospel?

At T4G Ligon Duncan addressed the topic of the Fathers and the Gospel: Did the Fathers Know the Gospel?  Good address.  Here's one of the texts he cited, from The Epistle to Diognetus:

He did not hate us, or reject us, or bear a grudge against us; instead he was patient and forbearing; in his mercy he took upon himself our sins; he himself gave up his own Son as a ransom for us, the holy one for the lawless, the guiltless for the guilty, the just for the unjust, the incorruptible for the corruptible, the immortal for the mortal.  For what else but his righteousness [dikaiosyne] could have covered our sins?  In whom was it possible for us, the lawless and ungodly, to be justified [dikaiothenai], except in the Son of God alone?  O the sweet exchange, O the incomprehensible work of God, O the unexpected blessings, that the sinfulness of many should be hidden in one righteous [dikaio] person, while the righteousness [dikaiosyne] of one should justify [dikaiose] many sinners! (Diogn. 9.3-5 [Holmes])

So did the Fathers know the gospel?  Well, yes.  Was their understanding as clear as it is now after hundreds and hundreds of years of the Church's interaction with sacred Scripture and going through the fires of controversy?  Well, no.  This is essentially what Duncan says.  What is of most interest to me with a text like the one quoted above is how close the language of justification actually is to the position of the reformers.  If The Epistle to Diognetus did not intend to teach imputation, it did a bad job of it.  Sounds Pauline and Lutheran to me.