The Argyle boss was thankful to French goalkeeper and club stalwart Romain Larrieu for keeping them in the tie with top-drawer saves at the end of each half.
Paul Mariner: "I am pleased that we are still in the competition because it is, in my opinion, the best domestic cup competition there is.
"A few weeks ago no-one would have backed us at home to the Championship leaders but at the moment it is all about progression for us at this club and that's now three games unbeaten, which is progress in my books.
"We are still in the competition, in the draw for the fourth round and have a trip to St James' Park in the cup to look forward to - and that's what we will be doing."