Rory McIlroy and Shane Lowry began their Zurich Classic title defence with a solid eight-under-par 64 in Thursday's opening round at TPC Louisiana.
The Irish pair, playing together for the first time since McIlroy completed his career Grand Slam at Augusta earlier this month, find themselves six shots behind the leaders after day one.
PGA Tour rookies Isaiah Salinda and Kevin Velo set a tournament record with a remarkable 58 in the better-ball format.
The defending champions will need to make up ground as they head into Friday's foursomes alternate shot format, with no team having successfully defended the Zurich Classic title.
Rory McIlroy revealed how Shane Lowry made a little joke over his form on Thursday
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Lowry carried the team during their front nine, with the Offaly man's score counting on seven of the nine holes in the fourball format.
He birdied the 10th, 11th, 13th and 18th as they reached the turn at four-under-par.
McIlroy then found his Augusta form on their second nine, birdieing the first before producing a fantastic eagle on the second hole to move the team to seven-under.
A Lowry birdie on the fourth was followed by bogeys on the sixth, before McIlroy's birdie on the par-five seventh secured their final score of eight-under.
The pair started at the 10th, playing the course "the wrong way round" according to reports.
Danish identical twins Nicolai and Rasmus Hojgaard sit one shot behind the leaders after carding an impressive 59.
Collin Morikawa and fellow American Kurt Kitayama are in the group sharing third place after firing a 61.
England's Matt Wallace and Danish partner Thorbjorn Olesen are a further stroke back.
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Rory McIlroy had a slow start to the Zurich Classic just days after winning The Masters
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England's Aaron Rai and American Sahith Theegala shot an opening 63.
The pairings of Scotland's Robert MacIntyre and Belgium's Thomas Detry, along with European Ryder Cup captain Luke Donald and Colombia's Camilo Villegas, share 28th spot with McIlroy and Lowry.
The tournament features fourball format on Thursday and Saturday, with foursomes on Friday and Sunday.
McIlroy joked about his slow start in his first competitive round since winning the Masters on 13 April.
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Shane Lowry had to save Rory McIlroy's bacon on the front-nine
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"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 35-year-old admitted he "didn't do anything" on their front nine before improving after the turn.
"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.
"It's important for us to obviously post a good score tomorrow."
