Starting the day at overnight 23rd place, Lahiri with a total of 212 slipped to tied-35th.
Andy Sullivan, who went into joint lead after first day, has stayed in sole lead thereafter.
Unable to find birdies the way he did during his 66-66 start on first two days, he still managed four-under 68 with a late burst that saw birdies on 15th and 17th holes.
Lahiri, who was in obvious discomfort because of his knee, where an old ailment to have flared up, said: "It was a weird day, as I struggled a bit with my knee."
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Lahiri faced some niggles with an old knee injury, which occurred some two years ago.
"I don't think it is bad, but I have to go and see it, when I get back. I have one more start and then I will get some good rest and work on my rehab," said Lahiri.
"As I said, I am not playing bad. I got six birdies, and missed a couple of makable birdie putts like on 17th from eight feet. You don't drop as many as six shots. You may drop a couple, but not six. And the golf course is not playing tough," he said.
On his overall play, Lahiri, winner of Malaysian Open and Hero Indian Open this year, said, "It was up and down. It was hard. I wasn't swinging too well to start with (but still had birdies on second and third). But from fifth to 14th, particularly it was so bad that I didn't even sniff a green and I missed so many regulations. Then over the last five holes, I made a couple of technical changes in my swing that took the pressure off my knee and it helped.
local golfer on the bag, opened with a bogey on the first, but back-to-back birdies raised visions of a upward move.
Thereafter, Lahiri bogeyed fourth and sixth, but got one back on ninth. After the turn, he dropped a bogey and a double on successive holes to suddenly go three-over for the day. But he salvaged the day with birdies on 14th, 16th and 18th before missing a birdie chance on 17th.
Meanwhile, Korea's An Byeong-Hun (66), leading the race to become the European Tour Rookie of the Year award, was tied fourth at 12-under and he was joined by Argentine Emiliano Grillo (71), who after being three-over through 14 holes, finished in style with four birdies on the trot to put himself back in contention.