Lowry, who won by six shots at Portrush in 2019 and has enjoyed a prolonged spell as champion due to last year’s event being cancelled because of the Covid-19 pandemic, was speaking after signing for a 69 in the third round at the Sandwich course.
Helped by two birdies and a “good par save” in the last three holes, the effort left him sitting around the top 10 on five-under, having opened with a 71 before showing his class with a second-round 65.
“I'm disappointed, to be honest,” admitted Lowry of his day’s work. “I think I missed four putts inside five feet, two of them were probably three feet or less. I probably should be closer to the leaders than I am. But I played great. Like tee to green I was as good as I've been all year. Today was similar to yesterday.
“I feel like I'm probably too far back. I feel like the leaders might go away from the field a little bit this evening. It's just so nice out there now. The course is pretty gettable. Yeah, there's a couple of tough flags, but you can get close to them if you're in position off the tee.
“I'm proud of myself how I battled. If I can go ahead and shoot five or six-under tomorrow, play the game golf I did today and manage to roll a few putts in, I think I can shoot that score.
Whether it will be good enough to win or not I don't know, but I'm probably a couple of shots short of where I want to be to have a chance to win.”
After finally being announced on the first tee as the defending champion, Lowry started bogey-bogey on Thursday, admitting he’d been “quite unnerved” by the second of those dropped shots after “stupidly” ignoring his game plan and hitting driver.
It’s been an impressive display since then, though, by the Clara man, who is coached by Neil Manchip. “Yeah, a pretty strong defence,” agreed Lowry.
“I got off to a pretty shaky start Thursday and battled well. I've been doing that all year. Any time I've kind of been the opposite side of a cut mark or my back is against the wall, I've been coming out of it very well.
“Mentally I've been good and I've been fighting very hard this year, and I feel like I'm playing great golf. I feel like if I put myself in position I can hit it close to most flags. My iron play feels quite good.”
Lowry tied for fourth behind Phil Mickelson in the US PGA Championship at Kiawah Island in May, having tied for 21st in the Masters then finished 65th in the US Open either side of that effort.
One big final push here and he could be edging ever closer to a Ryder Cup debut under the captaincy of close friend Harrington at Whistling Straits in September.
“Tomorrow is another big day for me, but every day feels like a big day, to be honest,” he said, smiling. “Every week you play is a huge event and tomorrow is no different going out in the final round of The Open.
“Look, I've got FedExCup, I've got Race to Dubai, I've got Ryder Cup, obviously, and I've got an Open Championship here to try and get my name in the mix on the back nine tomorrow afternoon.
“There's a lot on the line tomorrow, but I'm used to it by now, though. Look, I'd love to go out and shoot a good score and kind of not cement my place on the team but not be far away if I do that.”
Harrington, who had finished alongside Lowry in that US PGA Championship, saw his hopes of another high finish in this season’s majors dented by a double-bogey 6 at the last. That left him having to settle for a 73 and a three-over total.