Rory McIlroy tied second at Tour Championship

Northern Ireland's Rory McIlroy remains a shot off the lead after a three-under 67 in the second round of the season-ending Tour Championship in Atlanta.

The 30-year-old is tied for second with American Justin Thomas on 12 under, with US PGA Championship winner Brooks Koepka out in front on 13 under.

Thomas, who began the tournament five shots ahead of McIlroy because of a rankings-based system, carded a 68.

England's Paul Casey sits four shots off the lead on nine under after a 67.

McIlroy, who shot back-to-back birdies on his final two holes to take a share of second place, said he had “scrambled well” but admitted fortune had played its part.

“I got lucky on 18,” he told Sky Sports. “I just sort of rode my luck the whole way along that hole.

“Being three or four behind those guys for the most part of the day and then to catch Justin Thomas and only be one back of Brooks, it was nice to finish the way I did.”

The season-ending tournament uses an adapted sliding scale scoring format to decide the winner of the $15m (£12.3m) FedExCup first prize, a system McIlroy has raised questions about.

It meant Thomas started the week on 10 under and Koepka began on seven under, with McIlroy starting on five under.

Koepka, who also carded a 67, mixed four birdies – including a two-putt birdie on the par-five 18th – with a bogey.

But a weather delay interrupted his momentum and it was only at the last hole he was able to edge ahead.

McIlroy took better advantage of the 90-minute delay, firing his first birdie at the 12th before finishing his round with a 15-foot birdie putt on the 17th and a closing birdie on the 18th.