McIlroy bounced back from a four-over-par front nine of 40 to post a second consecutive one-under-par 71 on Friday to leave him at two under for the tournament at the halfway point.
That's still 12 strokes adrift of Spieth, who enjoys a five-shot lead over nearest challenger Charley Hoffman and is seven clear of the rest of the field having set a Masters record low score for 36 holes of 130.
That caught world number one McIlroy's attention as much as everybody else's but his rousing finish to Friday's play at Augusta National means he will tee off on Saturday with the belief that Spieth is catchable.
“It's really, really impressive,” McIlroy said of the 21-year-old Texan's performance. “I think a few guys can still catch him. It will take, obviously, something extraordinary from myself to get up there, but you never know. I know better than most people what can happen with the lead around here.
“But Jordan's had the experience. He had the experience last year. He had a couple-shot lead and couldn't quite hold on to it. But he'll have learned from that and he'll definitely handle it better this time around.”
McIlroy's own “almost” moment at the Masters came in 2011 when he let slip a four-shot lead while Spieth had a debut to remember here 12 months ago when he tied for the lead going into the final round only to see Bubba Watson take the Green Jacket.
“Really, I would need to shoot a 14 under par weekend and Jordan would have to play a couple average rounds,” the Irishman said, “and neither of those two things look like they're going to happen, so it's going to be tough.
“I'll go out and try and play the best that I can and we'll see where that leaves me. But, a few more nine holes like the one I just had there, you never know.”
Asked to explain his erratic scoring, which saw him card a double bogey, three bogeys and two birdies on the first nine, then an eagle, four birdies and one bogey on the second, McIlroy admitted: “You know, I don't know. Just, again, here, it's such a fine line. The margin for error is so small.
“Missing it in the wrong places sometimes and I missed a couple of really short putts back there, and that affected my confidence a little bit. But there's a few things like that.
“But the good golf is in there. It's just a matter of trying to get rid of the bad stuff, which was all on the front nine today.”
One thing that isn't affecting McIlroy's play, he insisted, was the expectation on his shoulders to win a career slam of the four majors, the Masters being the one remaining piece of the jigsaw.
“Not a factor at all,” he said. “No. I know, any of the bad golf, the bad shots I hit out there the last couple of days, I can't put that down to what it would mean or what I was playing for. I'm just trying to go out there and play the best golf I possibly can and that's about it.”