Lahiri added a second round 73 to the 72 he had on Thursday to get to three-over 145 but the cut was likely at even or one-over at the wet and damp Valhalla Golf Club.
Meanwhile, Rory McIlroy added a round of 67 to his first 66 and moved to nine-under and to the top, two shots clear of Ryan Palmer (65-70).
Lee Westwood and Kevin Chappell, two of the three overnight leaders - Palmer being the third - had just begun and were even par for first two holes.
Lahiri admitted making far too many mistakes and was also clearly somewhat rusty as he was still recovering from the illness and chicken pox suffered during the British Open three weeks ago.
"That's no excuse. Yes, I have not been 100 per cent but even then I should have played much better. I made far too many mistakes. Five bogeys in a round is way too many," he said.
