Rory McIlroy made a shocking start in his opening round at the WGC FedEx St Jude Invitational in Memphis, while Shane Lowry and Graeme McDowell enjoyed under par rounds to sit inside the top 15 at the end of the first day.

The Holywood native, playing in the afternoon on the opening day of the Tennessee event hit two bogeys on his front nine, however, things went from bad to worse for the four-time major winner.

Starting on the back nine, McIlroy made bogey on the 11th - after finding the water - and14th holes to turn at two over par, well down the field.

Without a birdie on his card by the time he arrived on the par three fourth hole - his 13th - McIlroy proceeded to make three bogeys in a row with a four on the fourth before dropping shots on the par four fifth and sixth holes.

By that stage, McIlroy was in a share of last place alongside Ryder Cup partner Ian Poulter, tied 77th in the 78-man field of the prestigious event.

McIlroy, needing a win to regain the world number one spot from Jon Rahm, finally gained a shot with birdie on his 16th hole to get back to four over par with one hole remaining.

And he pulled another shot back on 18 to give himself a much-needed boost heading into the second round to finish with two birdies inside the final three holes.

McIlroy ended the round in a share of 67th position, eleven shots off the leader, Brooks Koepka.

Shane Lowry and Graeme McDowell are also in the field this week and while the Open champion enjoyed a solid front nine, turning at two under par, following three birdies and a bogey, he handed the two shots back with a double bogey on the 11th hole.

The Offaly native got back under par on the 15th hole and then added another birdie on the 16th to move back to two under, finishing with a 68 to move inside the top 15.

McDowell, also starting on the back nine, made 13 pars in his opening 14 holes with just the one bogey on the par four 12th hole, his third.

The 2010 US Open champion then made his first birdie of the day on his 15th hole and added another on the next, before making it three in a row on his penultimate hole to join Lowry in a share of 15th place.

Brooks Koepka was back on top form as the four-time major winner moved clear of the field on eight under par, two shots clear of Rickie Fowler and Brendon Todd.