Northern Irish star McIlroy, chasing a second victory in his home open at The K Club, shot a bogey-free 68 to leave him tied for fourth place on 11 under par on Saturday.
Ahead of him are Frenchman Saddier, who also shot 68 to reach 15 under, Spaniard Hidalgo and McIlroy's playing partner Alfredo Garcia-Heredia, who outperformed the world No.2 by one stroke with two eagles in his 67 to reach 12 under.
But the round of the day belonged to Hidalgo, who carved up the front nine with seven successive birdies and made 12 in all - equalling the European tour record - in a stunning 63, despite recording a double-bogey at the 16th.
McIlroy's four birdies made for a subdued round by comparison and after ending the day level with second-round leader Joakim Lagergren, he told his caddie Harry Diamond when walking off the 18th green: "This is probably the most frustrating four-under-par round of golf I've played in a while."
McIlroy added: "I felt like I gave myself a lot of chances, hit some good putts that didn't go in. Had a nice one that dropped at 14. I feel like I could be a couple of shots better, but overall still in a decent position going into tomorrow.
"If I can get off to a fast start tomorrow and put a little bit of pressure on the guys behind, hopefully I'll be at the back nine in contention."
Hidalgo said of his breathtaking front nine: "I really felt for a few moments I was playing on the Playstation, to be honest. Every single shot was directly to the pin."
Elvis Smylie, the only Australian to make the cut, had a bright start, with three birdies in his first five holes, but eventually had to settle for a 70 which leaves him at two under for the tournament, tied for 30th.
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