By Derek Lawrenson for MailOnline Sergio Garcia leads at the halfway stage after a thrilling second round of the BMW Championship but worryingly for the revitalised Spaniard a familiar deadly foe has appeared in his rear view mirror. Rory McIlroy was well off the pace but a marvellous finish of three birdies in his last four holes for a second successive 67 has left him just two shots behind. Rory and Sergio has been a recurring theme this summer, of course, with the outcome to this point always the same. During the first two legs of his unforgettable treble, McIlroy defeated Garcia to claim the Open Championship at Hoylake and then the Bridgestone Invitational at Firestone.
@highlight
Sergio Garcia leads at the halfway stage on eight-under-par
@highlight
Rory McIlroy finished with three birdies in his last four holes
@highlight
Billy Horschel tied with McIlroy for third place on six under
Behind you: Leader @placeholder has Rory McIlroy in the chasing pack