Rory McIlroy and partner Shane Lowry shot a eight-under-par 64 which left them six off the pace as they began the defence of their Zurich Classic title.
In his first competitive round since winning the Masters and completing the career Grand Slam, McIlroy struggled on the opening nine as Lowry kept them in contention.
The pair started at the 10th and McIlroy said he “didn’t do anything” before improving after the turn when he birdied the first and eagled the second.
“Shane joked I could have got a couple extra hours in bed if I wanted to,” said McIlroy.
“I played a bit better coming in. It was OK.”
The Irish pair trail Isaiah Salinda and Kevin Velo who fired a 58 in the opening fourball round, which put them a stroke ahead of Danish brothers Rasmus and Nicolai Hojgaard.
