Having been in a five-way share of the first-round lead, McIlroy found himself four adrift of early starter Smith by the time he teed off in the afternoon.
The world number two swiftly wiped out that deficit with four birdies in his opening eight holes. His solitary dropped shot came at the 13th after an errant drive, but he immediately made amends.
“Once we turned for home the wind got its strongest for the day and it was hard to hit it close, quite a lot of crosswinds,” said McIlroy.
“I felt like I did well to hang on. Maybe could have been one or two better but overall it was a good day.”
Patrick Cantlay plummeted from overnight co-leader to a missed cut. Ludvig Aberg and Brooks Koepka also failed to make the weekend, while Jon Rahm squeezed through after a 65 lifted him to two under.
In contrast to Scheffler’s troubles, playing partner Fitzpatrick thrived to move within one of the lead. He is alongside 2021 Scottish Open champion Min Woo Lee on eight under.
Fitzpatrick, chasing a fourth win of the season, laid the groundwork with five birdies in a row from the 11th – his second hole – to charge up the leaderboard with a 65.
“Just felt like I did everything pretty solid. I feel fortunate enough to say that a lot this year,” said Fitzpatrick.
“This stretch of sort of March, February onwards to now, it’s definitely the best golf I’ve played in my career.”
Three back-nine birdies in succession helped home hero Bob MacIntyre to a 66 that leaves him two adrift.
Smith, the world number 82, benefited from a recent break as he outshone big names with the lowest round of the day.
“I had three weeks off, put the clubs away for a week and then came back re-energised and looking forward to this next stretch,” he said.
“Things are feeling good. I’m in a good mental space and just need to keep it going.”
