McIlroy and Lowry six off Zurich Classic pace

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.

With the Masters champion struggling on the opening nine as Lowry kept them in contention after they had started at the 10th, 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 after his first competitive round since completing the career Grand Slam at Augusta on 13 April.

"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.

"We felt like we left a few shots out there but we were just saying the two foursomes days on Friday and Sunday here are the important days in this tournament," added McIlroy, 35.

"It's important for us to obviously post a good score tomorrow."

Collin Morikawa and fellow US player Kurt Kitayama are in the group sharing third place after firing a 61, with England's Matt Wallace and partner Thorbjorn Olesen a further stroke back.

England's Aaron Rai and American Sahith Theegal shot an opening 63 with the pairings of Scotland's Robert MacIntyre and Belgium's Thomas Detry and European Ryder Cup captain Luke Donald and Colombia's Camilo Villegas sharing 28th spot with McIlroy and Lowry.

The reigning champions have never successfully defended the Zurich Classic title.