McIlroy carded his low round in the morning wave. He made the turn at 1-under and then went on a tear with five consecutive birdies to vault into the top spot.
The Northern Irishman, who won the tournament in 2018 and hasn't finished outside of the top-six in four straight appearances, credits his success at Bay Hill to learning from eight-time winner Tiger Woods.
"I've watched Tiger enough here over the years and the way he played this course was, he played it very conservatively," McIlroy said according to ASAP Sports. "He took care of the par-5s, and that was usually good enough to get the job done. So sort of take a little bit of a leaf out of his book."
Conners did a fantastic job tracking McIlroy down in the afternoon. The Canadian gained over 5.5 strokes through approach shots - the most in a single round for his career - and held the outright lead before three-putting his final hole to drop into a tie with McIlroy.
Bryson DeChambeau sits alone in third at 5-under. As expected, the beefy American leads the field in strokes gained: off the tee after Round 1.
Here's how the top of the leaderboard stands:
|Place||Player||To Par||R1 Score|
|T4||Byeong Hun An||-4||68|
Jordan Spieth shot 70 in his debut round at Bay Hill.
The field's scoring average on Day 1 was 73.11.
Round 2 from Bay Hill gets underway at 7 a.m. ET. Golf Channel's coverage starts at 2 p.m.