BMW Championship second round leaderboard:

-18 J Day (Aus); -13 D Berger (USA), B Todd (USA), -11 K Na (USA), J Spieth (USA), -10 G McNeill (USA), J Thomas (USA), S Piercy (USA). Selected others -9 R McIlroy (NIr), -8 J Rose, -6 P Casey (Eng), -4 I Poulter
Jason Day moved closer to claiming the world number one spot after opening up a five-shot lead after the second round of the BMW Championships in Chicago.
The Australian added a 63 to his opening 61 for a 36-hole total of 124 that tied the all-time PGA Tour record.
Day, at 18 under par, is well ahead of Americans Daniel Berger and Brendon Todd who are tied for second.
Jordan Spieth is seven shots behind after a five-under 66, while Rory McIlroy (65) is nine strokes back.
Day, who drained a 43-foot eagle putt at the last and is now 97 under par for his last 26 PGA Tour rounds, will usurp McIlroy as number one if he wins the tournament.
Englishman Justin Rose is a further shot back on eight under after a second-round 64.