McIlroy and Lowry team up to hold share of lead at Zurich Classic

A birdie on the 18th hole saw the pair, who both represented Ireland at the Tokyo Olympics three years ago, join three other pairings at the top of the leaderboard.

The tournament features fourball formats in the first and third rounds with alternate shots for the second and final rounds.

Also on 11-under were American pair Ben Kohles and Patton Kizzire, England's Aaron Rai and American David Lipsky and Americans Ryan Brehm and Mark Hubbard.

With a field lacking many of the tour's biggest names - world number one Scottie Scheffler is among the top players missing - the two major winners and Ryder Cup Europe players added some much-needed star power on the opening day.

McIlroy said that seeing some low scores from the early pairs had put a little pressure on him and Lowry.

"You know that you sort of need to get off to a good start, and thankfully we did. We were 4-under through four, which was really nice to see, and from there you've got some momentum and you're just trying to keep it going," said the world number two.

"But for the most part today, we kept both balls in play. We were having two looks basically on every hole at birdie, and that's the way you need to play better ball. Everyone thinks it's maybe a bit more gung ho than that, but as long as you have two balls in play off the tee, two balls on the green, I think you're always going to do pretty well in this format," he added.

McIlroy is making his debut in the tournament and said he is relishing the chance to make a push for a win with a team-mate he knows well.

"I don't know if I knew what to expect. I've watched this tournament a little bit over the years on TV, heard some good things from some of the players. It's nice to come here, team up with a really good friend, and if we play a good round tomorrow, it'll be awesome to be in contention for the weekend and try to get a win on the PGA Tour with a friend beside me. Looking forward to it," he said.

Nice vibe

Lowry, the 2019 British Open champion, said he felt a benefit to his game playing alongside McIlroy.

"I definitely felt today I was less hard on myself than I've been in the last few weeks when I hit a couple of bad shots. It's nice to know you've got Rory McIlroy backing you up.

"There's a nice vibe out there with the two of us," he added.

There was an unusual delay to play on the 17th hole at TPC Louisiana when an alligator strolled across the tee.

The groups of Bronson Burgoon and Jhonattan Vegas, along with Paul Barjon and Samuel Stevens, had to wait until the reptile had finished his journey before they could tee off the par-3 hole.

A trio of teams were a shot behind the leading quartet after shooting 10-under rounds of 62.

American duo Davis Thompson and Andrew Novak, Belgian Thomas Detry and Scotland's Robert MacIntyre and American Cameron Champ and South African MJ Daffue were all tied for second.

Eric Cole made an ace on the 207-yard par-3 14th, playing in a pairing with Russ Cochran. The 65-year-old Cochran was making his 600th PGA Tour appearance after Cole invited him to get off the 599 mark he had been sat on since his last tour event in 2013.